diff --git a/packages/core/database/migrations/2026_04_25_100000_add_tax_zone_id_to_carts_table.php b/packages/core/database/migrations/2026_04_25_100000_add_tax_zone_id_to_carts_table.php
new file mode 100644
index 0000000000..e6be248ae4
--- /dev/null
+++ b/packages/core/database/migrations/2026_04_25_100000_add_tax_zone_id_to_carts_table.php
@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+use Lunar\Base\Migration;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table($this->prefix.'carts', function (Blueprint $table) {
+            $table->foreignId('tax_zone_id')->after('channel_id')
+                ->nullable()
+                ->constrained($this->prefix.'tax_zones')
+                ->nullOnDelete();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table($this->prefix.'carts', function (Blueprint $table) {
+            if ($this->canDropForeignKeys()) {
+                $table->dropForeign(['tax_zone_id']);
+            }
+            $table->dropColumn('tax_zone_id');
+        });
+    }
+};
diff --git a/packages/core/src/Actions/Carts/CalculateLineSubtotal.php b/packages/core/src/Actions/Carts/CalculateLineSubtotal.php
index ca92eda51b..aa0a05c5b0 100644
--- a/packages/core/src/Actions/Carts/CalculateLineSubtotal.php
+++ b/packages/core/src/Actions/Carts/CalculateLineSubtotal.php
@@ -45,7 +45,7 @@ public function execute(
             );
 
             $priceInclTax = new Price(
-                $priceResponse->matched->priceIncTax()->value,
+                $priceResponse->matched->priceIncTax($cart->taxZone)->value,
                 $cart->currency,
                 $purchasable->getUnitQuantity()
             );
diff --git a/packages/core/src/Base/TaxDriver.php b/packages/core/src/Base/TaxDriver.php
index 3ce5af7417..8cb47da08d 100644
--- a/packages/core/src/Base/TaxDriver.php
+++ b/packages/core/src/Base/TaxDriver.php
@@ -5,6 +5,7 @@
 use Lunar\Base\ValueObjects\Cart\TaxBreakdown;
 use Lunar\Models\Contracts\CartLine;
 use Lunar\Models\Contracts\Currency;
+use Lunar\Models\Contracts\TaxZone;
 
 interface TaxDriver
 {
@@ -33,6 +34,15 @@ public function setPurchasable(Purchasable $purchasable): self;
      */
     public function setCartLine(CartLine $cartLine): self;
 
+    /**
+     * Set a tax zone override.
+     *
+     * When provided, this zone is used directly instead of resolving one from the shipping address, allowing
+     * the developer to handle cases like taxation on IP address basis. Just set the tax zone as and let it
+     * flow smoothly.
+     */
+    public function setTaxZone(?TaxZone $taxZone = null): self;
+
     /**
      * Return the tax breakdown from a given sub total.
      *
diff --git a/packages/core/src/Drivers/SystemTaxDriver.php b/packages/core/src/Drivers/SystemTaxDriver.php
index c29bf649ca..2eefa7b186 100644
--- a/packages/core/src/Drivers/SystemTaxDriver.php
+++ b/packages/core/src/Drivers/SystemTaxDriver.php
@@ -11,6 +11,7 @@
 use Lunar\DataTypes\Price;
 use Lunar\Models\Contracts\CartLine;
 use Lunar\Models\Contracts\Currency;
+use Lunar\Models\Contracts\TaxZone as TaxZoneContract;
 use Lunar\Models\TaxZone;
 use Spatie\LaravelBlink\BlinkFacade as Blink;
 
@@ -41,6 +42,12 @@ class SystemTaxDriver implements TaxDriver
      */
     protected ?CartLine $cartLine = null;
 
+    /**
+     * An optional tax zone override supplied at the cart level.
+     * When set this takes precedence over the address-derived zone.
+     */
+    protected ?TaxZoneContract $taxZone = null;
+
     /**
      * {@inheritDoc}
      */
@@ -91,12 +98,22 @@ public function setCartLine(CartLine $cartLine): self
         return $this;
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function setTaxZone(?TaxZoneContract $taxZone = null): self
+    {
+        $this->taxZone = $taxZone;
+
+        return $this;
+    }
+
     /**
      * {@inheritDoc}
      */
     public function getBreakdown($subTotal): TaxBreakdown
     {
-        $taxZone = app(GetTaxZone::class)->execute($this->shippingAddress);
+        $taxZone = $this->taxZone ?? app(GetTaxZone::class)->execute($this->shippingAddress);
         $taxClass = $this->purchasable->getTaxClass();
 
         $taxAmounts = Blink::once('tax_zone_rates_'.$taxZone->id.'_'.$taxClass->id, function () use ($taxClass, $taxZone) {
diff --git a/packages/core/src/Models/Cart.php b/packages/core/src/Models/Cart.php
index e562fd76df..f5197d1200 100644
--- a/packages/core/src/Models/Cart.php
+++ b/packages/core/src/Models/Cart.php
@@ -42,6 +42,7 @@
 use Lunar\Exceptions\FingerprintMismatchException;
 use Lunar\Facades\DB;
 use Lunar\Facades\ShippingManifest;
+use Lunar\Models\Contracts\TaxZone as TaxZoneContract;
 use Lunar\Pipelines\Cart\Calculate;
 use Lunar\Validation\Cart\ValidateCartForOrderCreation;
 use Lunar\Validation\CartLine\CartLineStock;
@@ -53,6 +54,7 @@
  * @property ?int $merged_id
  * @property int $currency_id
  * @property int $channel_id
+ * @property ?int $tax_zone_id
  * @property ?int $order_id
  * @property ?string $coupon_code
  * @property ?Carbon $completed_at
@@ -230,6 +232,11 @@ public function customer(): BelongsTo
         return $this->belongsTo(Customer::modelClass());
     }
 
+    public function taxZone(): BelongsTo
+    {
+        return $this->belongsTo(TaxZone::modelClass());
+    }
+
     public function scopeUnmerged(Builder $query): Builder
     {
         return $query->whereNull('merged_id');
@@ -493,8 +500,12 @@ public function addAddress(array|Addressable $address, string $type, bool $refre
             ->then(fn () => $refresh ? $this->refresh()->recalculate() : $this);
     }
 
-    public function setShippingAddress(array|Addressable $address): Cart
+    public function setShippingAddress(array|Addressable $address, bool $clearTaxZone = true): Cart
     {
+        if ($clearTaxZone && $this->tax_zone_id) {
+            $this->taxZone()->dissociate()->save();
+        }
+
         return $this->addAddress($address, 'shipping');
     }
 
@@ -622,4 +633,28 @@ public function getEstimatedShipping(array $params, bool $setOverride = false):
 
         return $option;
     }
+
+    /**
+     * Set the tax zone override for this cart.
+     *
+     * When set, all tax calculations use this zone instead of resolving one from the shipping address.
+     * Pass null to clear the override and fall back to the address-derived (or default) zone.
+     * Pass `$refresh = false` to skip persistence and recalculation (useful for previewing without writing).
+     */
+    public function setTaxZone(?TaxZoneContract $taxZone, bool $refresh = true): Cart
+    {
+        if ($taxZone) {
+            $this->taxZone()->associate($taxZone);
+        } else {
+            $this->taxZone()->dissociate();
+        }
+
+        if (! $refresh) {
+            return $this;
+        }
+
+        $this->save();
+
+        return $this->refresh()->recalculate();
+    }
 }
diff --git a/packages/core/src/Models/CartLine.php b/packages/core/src/Models/CartLine.php
index 4571e70e8f..f50e026cc4 100644
--- a/packages/core/src/Models/CartLine.php
+++ b/packages/core/src/Models/CartLine.php
@@ -41,6 +41,7 @@ class CartLine extends BaseModel implements Contracts\CartLine
      */
     public $cachableProperties = [
         'unitPrice',
+        'unitPriceInclTax',
         'subTotal',
         'discountTotal',
         'taxAmount',
diff --git a/packages/core/src/Models/Contracts/Cart.php b/packages/core/src/Models/Contracts/Cart.php
index 04ef4578d0..1528134243 100644
--- a/packages/core/src/Models/Contracts/Cart.php
+++ b/packages/core/src/Models/Contracts/Cart.php
@@ -139,8 +139,12 @@ public function addAddress(array|Addressable $address, string $type, bool $refre
 
     /**
      * Set the shipping address.
+     *
+     * By default any tax-zone override set on the cart is cleared, since
+     * the address is now the authoritative source for tax-zone resolution.
+     * Pass `$clearTaxZone = false` to keep a previously-pinned zone.
      */
-    public function setShippingAddress(array|Addressable $address): \Lunar\Models\Cart;
+    public function setShippingAddress(array|Addressable $address, bool $clearTaxZone = true): \Lunar\Models\Cart;
 
     /**
      * Set the billing address.
@@ -188,4 +192,13 @@ public function checkFingerprint(string $fingerprint): bool;
      * Return the estimated shipping cost for a cart.
      */
     public function getEstimatedShipping(array $params, bool $setOverride = false): ?ShippingOption;
+
+    /**
+     * Set the tax zone override for this cart.
+     *
+     * When set, all tax calculations use this zone instead of resolving one
+     * from the shipping address. Pass null to clear the override.
+     * Pass `$refresh = false` to skip persistence and recalculation.
+     */
+    public function setTaxZone(?TaxZone $taxZone, bool $refresh = true): \Lunar\Models\Cart;
 }
diff --git a/packages/core/src/Models/Contracts/Price.php b/packages/core/src/Models/Contracts/Price.php
index 38781074c2..49ea35daa8 100644
--- a/packages/core/src/Models/Contracts/Price.php
+++ b/packages/core/src/Models/Contracts/Price.php
@@ -4,6 +4,7 @@
 
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\MorphTo;
+use Lunar\Models\Contracts\TaxZone;
 
 interface Price
 {
@@ -24,11 +25,22 @@ public function customerGroup(): BelongsTo;
 
     /**
      * Return the price exclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone
      */
-    public function priceExTax(): \Lunar\DataTypes\Price;
+    public function priceExTax(?TaxZone $taxZone = null): \Lunar\DataTypes\Price;
 
     /**
      * Return the price inclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone
      */
-    public function priceIncTax(): int|\Lunar\DataTypes\Price;
+    public function priceIncTax(?TaxZone $taxZone = null): int|\Lunar\DataTypes\Price;
+
+    /**
+     * Return the compare price inclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone
+     */
+    public function comparePriceIncTax(?TaxZone $taxZone = null): int|\Lunar\DataTypes\Price;
 }
diff --git a/packages/core/src/Models/Price.php b/packages/core/src/Models/Price.php
index 76e960cbb7..c6e1e286e2 100644
--- a/packages/core/src/Models/Price.php
+++ b/packages/core/src/Models/Price.php
@@ -10,6 +10,7 @@
 use Lunar\Base\Casts\Price as CastsPrice;
 use Lunar\Base\Traits\HasMacros;
 use Lunar\Database\Factories\PriceFactory;
+use Lunar\Models\Contracts\TaxZone as TaxZoneContract;
 use Spatie\LaravelBlink\BlinkFacade as Blink;
 
 /**
@@ -76,8 +77,10 @@ public function customerGroup(): BelongsTo
 
     /**
      * Return the price exclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone  Optional override for the tax zone. Falls back to the store's default zone.
      */
-    public function priceExTax(): \Lunar\DataTypes\Price
+    public function priceExTax(?TaxZoneContract $taxZone = null): \Lunar\DataTypes\Price
     {
         if (! prices_inc_tax()) {
             return $this->price;
@@ -85,50 +88,60 @@ public function priceExTax(): \Lunar\DataTypes\Price
 
         $priceExTax = clone $this->price;
 
-        $priceExTax->value = (int) round($priceExTax->value / (1 + $this->getPriceableTaxRate()));
+        $priceExTax->value = (int) round($priceExTax->value / (1 + $this->getPriceableTaxRate($taxZone)));
 
         return $priceExTax;
     }
 
     /**
      * Return the price inclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone  Optional override for the tax zone.
      */
-    public function priceIncTax(): int|\Lunar\DataTypes\Price
+    public function priceIncTax(?TaxZoneContract $taxZone = null): int|\Lunar\DataTypes\Price
     {
         if (prices_inc_tax()) {
             return $this->price;
         }
 
         $priceIncTax = clone $this->price;
-        $priceIncTax->value = (int) round($priceIncTax->value * (1 + $this->getPriceableTaxRate()));
+        $priceIncTax->value = (int) round($priceIncTax->value * (1 + $this->getPriceableTaxRate($taxZone)));
 
         return $priceIncTax;
     }
 
     /**
      * Return the compare price inclusive of tax.
+     *
+     * @param  TaxZone|null  $taxZone  Optional override for the tax zone.
      */
-    public function comparePriceIncTax(): int|\Lunar\DataTypes\Price
+    public function comparePriceIncTax(?TaxZoneContract $taxZone = null): int|\Lunar\DataTypes\Price
     {
         if (prices_inc_tax()) {
             return $this->compare_price;
         }
 
         $comparePriceIncTax = clone $this->compare_price;
-        $comparePriceIncTax->value = (int) round($comparePriceIncTax->value * (1 + $this->getPriceableTaxRate()));
+        $comparePriceIncTax->value = (int) round($comparePriceIncTax->value * (1 + $this->getPriceableTaxRate($taxZone)));
 
         return $comparePriceIncTax;
     }
 
     /**
-     * Return the total tax rate amount within the predefined tax zone for the related priceable
+     * Return the total tax rate (as a decimal, e.g. 0.20 = 20%) for the given tax zone
+     * combined with the priceable's own tax class.
+     *
+     * Tax zone resolution: explicit param → store default zone.
+     * Results are memoised per "{classId}_{zoneId}" so unrelated combinations never collide.
      */
-    protected function getPriceableTaxRate(): int|float
+    protected function getPriceableTaxRate(?TaxZoneContract $taxZone = null): int|float
     {
-        return Blink::once('price_tax_rate_'.$this->priceable->getTaxClass()->id, function () {
-            $taxZone = TaxZone::where('default', '=', 1)->first();
+        $taxClass = $this->priceable->getTaxClass();
+        $taxZone ??= Blink::once('lunar_default_tax_zone', fn () => TaxZone::where('default', '=', 1)->first());
+        $cacheKey = 'price_tax_rate_'.$taxClass->id.'_'.($taxZone?->id ?? 'none');
 
-            if ($taxZone && ! is_null($taxClass = $this->priceable->getTaxClass())) {
+        return Blink::once($cacheKey, function () use ($taxClass, $taxZone) {
+            if ($taxZone && $taxClass) {
                 return $taxClass->taxRateAmounts
                     ->whereIn('tax_rate_id', $taxZone->taxRates->pluck('id'))
                     ->sum('percentage') / 100;
diff --git a/packages/core/src/Pipelines/Cart/CalculateTax.php b/packages/core/src/Pipelines/Cart/CalculateTax.php
index bc83324f15..b7b964e01c 100644
--- a/packages/core/src/Pipelines/Cart/CalculateTax.php
+++ b/packages/core/src/Pipelines/Cart/CalculateTax.php
@@ -37,6 +37,7 @@ public function handle(CartContract $cart, Closure $next): mixed
                 ->setCurrency($cart->currency)
                 ->setPurchasable($cartLine->purchasable)
                 ->setCartLine($cartLine)
+                ->setTaxZone($cart->taxZone)
                 ->getBreakdown($subTotal);
 
             $taxBreakDownAmounts = $taxBreakDownAmounts->merge(
@@ -70,6 +71,7 @@ public function handle(CartContract $cart, Closure $next): mixed
             $shippingTax = Taxes::setShippingAddress($cart->shippingAddress)
                 ->setCurrency($cart->currency)
                 ->setPurchasable($shippingOption)
+                ->setTaxZone($cart->taxZone)
                 ->getBreakdown($shippingSubTotal);
 
             $shippingTaxTotal = $shippingTax->amounts->sum('price.value');
diff --git a/packages/core/src/Pipelines/CartLine/GetUnitPrice.php b/packages/core/src/Pipelines/CartLine/GetUnitPrice.php
index 7bfde0f20d..da77934b90 100644
--- a/packages/core/src/Pipelines/CartLine/GetUnitPrice.php
+++ b/packages/core/src/Pipelines/CartLine/GetUnitPrice.php
@@ -47,7 +47,7 @@ public function handle(CartLineContract $cartLine, Closure $next)
         );
 
         $cartLine->unitPriceInclTax = new Price(
-            $priceResponse->matched->priceIncTax()->value,
+            $priceResponse->matched->priceIncTax($cart->taxZone)->value,
             $cart->currency,
             $purchasable->getUnitQuantity()
         );
diff --git a/tests/core/Feature/Drivers/SystemTaxDriverTest.php b/tests/core/Feature/Drivers/SystemTaxDriverTest.php
index bb01da059e..3a1e0b8bac 100644
--- a/tests/core/Feature/Drivers/SystemTaxDriverTest.php
+++ b/tests/core/Feature/Drivers/SystemTaxDriverTest.php
@@ -123,6 +123,86 @@
     expect($breakdown->amounts[0]->price->value)->toEqual(166);
 });
 
+test('can set tax zone', function () {
+    $taxZone = TaxZone::factory()->create();
+
+    $driver = (new SystemTaxDriver)
+        ->setTaxZone($taxZone);
+
+    expect($driver)->toBeInstanceOf(SystemTaxDriver::class);
+});
+
+test('uses cart tax zone override instead of default zone', function () {
+    $address = Address::factory()->create();
+    $currency = Currency::factory()->create();
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create();
+    $overrideTaxZone = TaxZone::factory()->state(['default' => false])->create();
+
+    $taxClass = TaxClass::factory()->create();
+
+    // Default zone: 20 %
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create()->id,
+        'percentage' => 20,
+    ]);
+
+    // Override zone: 5 %
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => TaxRate::factory()->state(['tax_zone_id' => $overrideTaxZone])->create()->id,
+        'percentage' => 5,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+    $line = CartLine::factory(['purchasable_id' => $variant->id])->create();
+
+    $breakdown = (new SystemTaxDriver)
+        ->setShippingAddress($address)
+        ->setBillingAddress($address)
+        ->setCurrency($currency)
+        ->setPurchasable($variant)
+        ->setCartLine($line)
+        ->setTaxZone($overrideTaxZone)
+        ->getBreakdown(1000);
+
+    // 5 % of 1000 = 50, not 20 % = 200
+    expect($breakdown)->toBeInstanceOf(TaxBreakdown::class);
+    expect($breakdown->amounts->count())->toEqual(1);
+    expect($breakdown->amounts[0]->price->value)->toEqual(50);
+});
+
+test('falls back to address-derived zone when no override is set', function () {
+    $address = Address::factory()->create();
+    $currency = Currency::factory()->create();
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create();
+
+    $taxClass = TaxClass::factory()->create();
+
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create()->id,
+        'percentage' => 20,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+    $line = CartLine::factory(['purchasable_id' => $variant->id])->create();
+
+    // No setTaxZone() call
+    $breakdown = (new SystemTaxDriver)
+        ->setShippingAddress($address)
+        ->setBillingAddress($address)
+        ->setCurrency($currency)
+        ->setPurchasable($variant)
+        ->setCartLine($line)
+        ->getBreakdown(1000);
+
+    // Should use address-derived (default) zone → 20 %
+    expect($breakdown)->toBeInstanceOf(TaxBreakdown::class);
+    expect($breakdown->amounts->count())->toEqual(1);
+    expect($breakdown->amounts[0]->price->value)->toEqual(200);
+});
+
 test('can get breakdown with correct tax zone', function () {
     $address = Address::factory()->create();
     $currency = Currency::factory()->create();
diff --git a/tests/core/Stubs/TestTaxDriver.php b/tests/core/Stubs/TestTaxDriver.php
index 2e4fa299e6..23e375452b 100644
--- a/tests/core/Stubs/TestTaxDriver.php
+++ b/tests/core/Stubs/TestTaxDriver.php
@@ -10,6 +10,7 @@
 use Lunar\DataTypes\Price;
 use Lunar\Models\Contracts\CartLine as CartLineContract;
 use Lunar\Models\Contracts\Currency as CurrencyContract;
+use Lunar\Models\Contracts\TaxZone as TaxZoneContract;
 use Lunar\Models\Currency;
 use Lunar\Models\ProductVariant;
 use Lunar\Models\TaxRateAmount;
@@ -41,6 +42,11 @@ class TestTaxDriver implements TaxDriver
      */
     protected CartLineContract $cartLine;
 
+    /**
+     * The optional tax zone override.
+     */
+    protected ?TaxZoneContract $taxZone = null;
+
     /**
      * {@inheritDoc}
      */
@@ -91,6 +97,16 @@ public function setCartLine(CartLineContract $cartLine): self
         return $this;
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function setTaxZone(?TaxZoneContract $taxZone = null): self
+    {
+        $this->taxZone = $taxZone;
+
+        return $this;
+    }
+
     /**
      * {@inheritDoc}
      */
@@ -100,7 +116,14 @@ public function getBreakdown($subTotal): TaxBreakdown
 
         if ($this->purchasable) {
             $taxClass = $this->purchasable->getTaxClass();
-            $taxAmounts = $taxClass->taxRateAmounts;
+
+            // When a zone override is provided, restrict to that zone's rate amounts
+            // (mirrors SystemTaxDriver behaviour so cart-level zone tests work correctly).
+            if ($this->taxZone) {
+                $taxAmounts = $this->taxZone->taxAmounts()->whereTaxClassId($taxClass->id)->get();
+            } else {
+                $taxAmounts = $taxClass->taxRateAmounts;
+            }
         } else {
             $taxAmounts = TaxRateAmount::factory(2)->create();
         }
diff --git a/tests/core/Unit/Models/CartTest.php b/tests/core/Unit/Models/CartTest.php
index 0d941413a8..18bab4d905 100644
--- a/tests/core/Unit/Models/CartTest.php
+++ b/tests/core/Unit/Models/CartTest.php
@@ -1167,6 +1167,90 @@
 
 });
 
+test('cart tax zone override is applied through the full calculation pipeline', function () {
+    // Prices are stored ex-tax; tax is added on top during cart calculation.
+    Config::set('lunar.pricing.stored_inclusive_of_tax', false);
+
+    $currency = Currency::factory()->state(['code' => 'GBP'])->create();
+    $cart = Cart::factory()->create(['currency_id' => $currency->id]);
+
+    $taxClass = TaxClass::factory()->create(['name' => 'Standard', 'default' => true]);
+
+    // Default zone: 0 % – simulates a store where no tax applies for unknown locations.
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create();
+    $defaultRate = TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create(['name' => 'Default Rate']);
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $defaultRate->id,
+        'percentage' => 0,
+    ]);
+
+    // UAE zone: 20 % – the override set by IP-detection middleware.
+    $uaeZone = TaxZone::factory()->state(['default' => false])->create(['name' => 'UAE']);
+    $uaeRate = TaxRate::factory()->state(['tax_zone_id' => $uaeZone])->create(['name' => 'UAE VAT']);
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $uaeRate->id,
+        'percentage' => 20,
+    ]);
+
+    $purchasable = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+
+    Price::factory()->create([
+        'price' => 1000,
+        'min_quantity' => 1,
+        'currency_id' => $currency->id,
+        'priceable_type' => $purchasable->getMorphClass(),
+        'priceable_id' => $purchasable->id,
+    ]);
+
+    $cart->lines()->create([
+        'purchasable_type' => $purchasable->getMorphClass(),
+        'purchasable_id' => $purchasable->id,
+        'quantity' => 1,
+    ]);
+
+    // Default zone (0 %) – the cart-level zone is passed through the full pipeline:
+    // CalculateLines publishes the Blink key; CalculateTax forwards it to the driver.
+    $cart->setTaxZone($defaultTaxZone)->calculate();
+    expect($cart->taxTotal->value)->toEqual(0);
+    expect($cart->total->value)->toEqual(1000);
+
+    // Switch to UAE zone (20 %) – the override is correctly picked up.
+    $cart->setTaxZone($uaeZone)->recalculate();
+    expect($cart->taxTotal->value)->toEqual(200);   // 20 % of 1000
+    expect($cart->total->value)->toEqual(1200);
+
+    // Switch back to the default zone – pipeline correctly reverts to 0 %.
+    $cart->setTaxZone($defaultTaxZone)->recalculate();
+    expect($cart->taxTotal->value)->toEqual(0);
+    expect($cart->total->value)->toEqual(1000);
+});
+
+test('setShippingAddress clears the tax zone override by default', function () {
+    $currency = Currency::factory()->create();
+    $cart = Cart::factory()->create(['currency_id' => $currency->id]);
+
+    $taxZone = TaxZone::factory()->state(['default' => false])->create();
+    $cart->setTaxZone($taxZone, refresh: false)->save();
+
+    $cart->setShippingAddress(CartAddress::factory()->make()->toArray());
+
+    expect($cart->fresh()->tax_zone_id)->toBeNull();
+});
+
+test('setShippingAddress preserves the tax zone override when opted out', function () {
+    $currency = Currency::factory()->create();
+    $cart = Cart::factory()->create(['currency_id' => $currency->id]);
+
+    $taxZone = TaxZone::factory()->state(['default' => false])->create();
+    $cart->setTaxZone($taxZone, refresh: false)->save();
+
+    $cart->setShippingAddress(CartAddress::factory()->make()->toArray(), clearTaxZone: false);
+
+    expect($cart->fresh()->tax_zone_id)->toEqual($taxZone->id);
+});
+
 test('active scope correctly filters unmerged carts and isolates users', function () {
     setAuthUserConfig();
 
diff --git a/tests/core/Unit/Models/PriceTest.php b/tests/core/Unit/Models/PriceTest.php
index 7a05469519..123ece1b50 100644
--- a/tests/core/Unit/Models/PriceTest.php
+++ b/tests/core/Unit/Models/PriceTest.php
@@ -3,10 +3,16 @@
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Illuminate\Support\Facades\Config;
 use Lunar\DataTypes\Price as DataTypesPrice;
+use Lunar\Models\Country;
 use Lunar\Models\Currency;
 use Lunar\Models\CustomerGroup;
 use Lunar\Models\Price;
 use Lunar\Models\ProductVariant;
+use Lunar\Models\TaxClass;
+use Lunar\Models\TaxRate;
+use Lunar\Models\TaxRateAmount;
+use Lunar\Models\TaxZone;
+use Lunar\Models\TaxZoneCountry;
 use Lunar\Tests\Core\TestCase;
 
 uses(TestCase::class);
@@ -294,3 +300,185 @@ function can_handle_non_int_values()
 
     expect($price->comparePriceIncTax()->value)->toEqual(2000);
 });
+
+test('priceIncTax falls back to the default tax zone when no zone is given', function () {
+    Config::set('lunar.pricing.stored_inclusive_of_tax', false);
+
+    $currency = Currency::factory()->create([
+        'code' => 'GBP',
+        'decimal_places' => 2,
+        'default' => true,
+    ]);
+
+    $taxClass = TaxClass::factory()->create();
+
+    // Default zone: 0 %
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create();
+    $defaultRate = TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $defaultRate->id,
+        'percentage' => 0,
+    ]);
+
+    // Override zone: 20 %
+    $overrideZone = TaxZone::factory()->state(['default' => false])->create();
+    $overrideRate = TaxRate::factory()->state(['tax_zone_id' => $overrideZone])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $overrideRate->id,
+        'percentage' => 20,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+
+    $price = Price::factory()->create([
+        'currency_id' => $currency->id,
+        'priceable_id' => $variant->id,
+        'priceable_type' => $variant->getMorphClass(),
+        'price' => 1000,
+        'min_quantity' => 1,
+    ]);
+
+    // No param → falls back to the store's default zone (0 %).
+    expect($price->priceIncTax()->value)->toEqual(1000);
+
+    // Explicit override zone → 20 % applies.
+    expect($price->priceIncTax($overrideZone)->value)->toEqual(1200);
+});
+
+test('priceIncTax explicit taxZone param overrides the default zone', function () {
+    // Prices stored ex-tax.
+    Config::set('lunar.pricing.stored_inclusive_of_tax', false);
+
+    $currency = Currency::factory()->create(['code' => 'AED', 'decimal_places' => 2, 'default' => true]);
+
+    $taxClass = TaxClass::factory()->create(['name' => 'Standard']);
+
+    // Zone A: 5 % (default)
+    $zoneA = TaxZone::factory()->state(['default' => true])->create(['name' => 'Zone A']);
+    $rateA = TaxRate::factory()->state(['tax_zone_id' => $zoneA])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $rateA->id,
+        'percentage' => 5,
+    ]);
+
+    // Zone B: 20 %
+    $zoneB = TaxZone::factory()->state(['default' => false])->create(['name' => 'Zone B']);
+    $rateB = TaxRate::factory()->state(['tax_zone_id' => $zoneB])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $rateB->id,
+        'percentage' => 20,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+    $price = Price::factory()->create([
+        'currency_id' => $currency->id,
+        'priceable_id' => $variant->id,
+        'priceable_type' => $variant->getMorphClass(),
+        'price' => 1000,
+        'min_quantity' => 1,
+    ]);
+
+    // Default would resolve to Zone A (5 %), but explicit Zone B (20 %) must win.
+    expect($price->priceIncTax(taxZone: $zoneB)->value)->toEqual(1200);
+
+    // Also works on priceExTax (prices stored inc-tax scenario)
+    Config::set('lunar.pricing.stored_inclusive_of_tax', true);
+    $priceInc = Price::factory()->create([
+        'currency_id' => $currency->id,
+        'priceable_id' => $variant->id,
+        'priceable_type' => $variant->getMorphClass(),
+        'price' => 1200,   // stored inc 20 %
+        'min_quantity' => 1,
+    ]);
+    expect($priceInc->priceExTax(taxZone: $zoneB)->value)->toEqual(1000);
+});
+
+test('priceIncTax accepts an explicit tax zone param', function () {
+    Config::set('lunar.pricing.stored_inclusive_of_tax', false);
+
+    $currency = Currency::factory()->create(['code' => 'AED', 'decimal_places' => 2, 'default' => true]);
+
+    // Default zone: 0 % (global default for unknown locations)
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create(['name' => 'Default']);
+    $defaultTaxClass = TaxClass::factory()->create(['name' => 'Default', 'default' => true]);
+    $defaultRate = TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $defaultTaxClass->id,
+        'tax_rate_id' => $defaultRate->id,
+        'percentage' => 0,
+    ]);
+
+    // UAE zone: 10 % VAT
+    $uaeZone = TaxZone::factory()->state(['default' => false])->create(['name' => 'UAE']);
+    $uae = Country::factory()->create(['iso3' => 'ARE', 'name' => 'United Arab Emirates']);
+    TaxZoneCountry::factory()->create(['tax_zone_id' => $uaeZone->id, 'country_id' => $uae->id]);
+    $uaeRate = TaxRate::factory()->state(['tax_zone_id' => $uaeZone])->create(['name' => 'UAE VAT']);
+    $vatTaxClass = TaxClass::factory()->create(['name' => 'UAE VAT 10%']);
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $vatTaxClass->id,
+        'tax_rate_id' => $uaeRate->id,
+        'percentage' => 10,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $vatTaxClass->id])->create();
+    $price = Price::factory()->create([
+        'currency_id' => $currency->id,
+        'priceable_id' => $variant->id,
+        'priceable_type' => $variant->getMorphClass(),
+        'price' => 1000,
+        'min_quantity' => 1,
+    ]);
+
+    // Without zone override – falls back to default zone → 0 % even though
+    // the variant's class has UAE rates configured
+    expect($price->priceIncTax()->value)->toEqual(1000);
+
+    // Passing the UAE zone explicitly returns the 10 % rate for that zone
+    expect($price->priceIncTax(taxZone: $uaeZone)->value)->toEqual(1100);
+});
+
+test('comparePriceIncTax accepts explicit taxZone param', function () {
+    Config::set('lunar.pricing.stored_inclusive_of_tax', false);
+
+    $currency = Currency::factory()->create(['code' => 'AED', 'decimal_places' => 2, 'default' => true]);
+
+    $taxClass = TaxClass::factory()->create(['default' => true]);
+
+    // Default zone: 0 %
+    $defaultTaxZone = TaxZone::factory()->state(['default' => true])->create();
+    $defaultRate = TaxRate::factory()->state(['tax_zone_id' => $defaultTaxZone])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $defaultRate->id,
+        'percentage' => 0,
+    ]);
+
+    // UAE zone: 10 %
+    $uaeZone = TaxZone::factory()->state(['default' => false])->create(['name' => 'UAE']);
+    $uaeRate = TaxRate::factory()->state(['tax_zone_id' => $uaeZone])->create();
+    TaxRateAmount::factory()->create([
+        'tax_class_id' => $taxClass->id,
+        'tax_rate_id' => $uaeRate->id,
+        'percentage' => 10,
+    ]);
+
+    $variant = ProductVariant::factory(['tax_class_id' => $taxClass->id])->create();
+    $price = Price::factory()->create([
+        'currency_id' => $currency->id,
+        'priceable_id' => $variant->id,
+        'priceable_type' => $variant->getMorphClass(),
+        'price' => 1000,
+        'compare_price' => 1500,
+        'min_quantity' => 1,
+    ]);
+
+    // Default zone → 0 % on compare price
+    expect($price->comparePriceIncTax()->value)->toEqual(1500);
+
+    // UAE zone → 10 % on compare price
+    expect($price->comparePriceIncTax(taxZone: $uaeZone)->value)->toEqual(1650);
+});