fix(billing): VAT follows the customer, not a global setting

Codex was right that this could misstate real charges: an EU business with a
VAT ID registered in another country is billed under reverse charge, and we
were adding 20 % Austrian VAT to their total anyway. TaxTreatment resolves it
from the customer's VAT ID, and the whole page — cart, plan cards, add-on
cards — now states one treatment instead of contradicting itself.

Explicitly NOT handled: cross-border sales to private individuals, which are
taxed at the buyer's national rate under OSS. That needs a maintained rate
table and a tax adviser, not a guess, so those fall back to the domestic rate —
over-collecting rather than under-collecting.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Livewire/Billing.php

@@ -122,6 +122,9 @@ class Billing extends Component
             'upgrades' => $upgrades,
             'storage' => (array) config('provisioning.storage_addon'),
             'trafficAddon' => (array) config('provisioning.traffic.addon'),
+            // Resolved once: the cart and the plan cards must not state
+            // different tax treatments on the same page.
+            'tax' => \App\Services\Billing\TaxTreatment::for($customer),
             'trafficMeter' => $instance !== null ? \App\Services\Traffic\TrafficMeter::for($instance) : null,
             'addons' => (array) config('provisioning.addons'),
             'pending' => $customer

app/Models/Order.php

@@ -3,6 +3,7 @@
 namespace App\Models;
 
 use App\Models\Concerns\HasUuid;
+use App\Services\Billing\TaxTreatment;
 use App\Provisioning\Contracts\ProvisioningSubject;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
@@ -54,15 +55,18 @@ class Order extends Model implements ProvisioningSubject
         return $this->type !== 'traffic';
     }
 
-    /** Net is what is stored; gross is what gets charged. */
+    /**
+     * Net is what is stored; gross is what gets charged — and how much VAT that
+     * is depends on the customer, not on a global setting.
+     */
     public function grossCents(): int
     {
-        return (int) round($this->amount_cents * (1 + self::taxRate()));
+        return $this->taxTreatment()->grossCents($this->amount_cents);
     }
 
-    public static function taxRate(): float
+    public function taxTreatment(): TaxTreatment
     {
-        return (float) config('provisioning.tax.rate_percent', 0) / 100;
+        return TaxTreatment::for($this->customer);
     }
 
     /** Only a pending order is still the customer's to change. */

app/Services/Billing/TaxTreatment.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace App\Services\Billing;
+
+use App\Models\Customer;
+
+/**
+ * Which VAT applies to a customer, and why.
+ *
+ * Only the two clear-cut cases are decided here:
+ *
+ *  - a customer with a VAT ID registered in another EU country pays no VAT to
+ *    us; the liability shifts to them (reverse charge), and the invoice has to
+ *    say so;
+ *  - everyone else is charged the seller's domestic rate.
+ *
+ * Deliberately NOT handled: cross-border sales to private individuals, which
+ * are taxed at the customer's own country's rate under the OSS scheme. Doing
+ * that needs a maintained rate table per member state and a tax adviser's sign
+ * off, not a guess in a config file — so those customers fall back to the
+ * domestic rate, which over-collects rather than under-collects.
+ */
+final readonly class TaxTreatment
+{
+    private function __construct(
+        public float $rate,
+        public bool $reverseCharge,
+    ) {}
+
+    public static function for(?Customer $customer): self
+    {
+        $domestic = (float) config('provisioning.tax.rate_percent', 0) / 100;
+
+        $vatId = strtoupper(preg_replace('/\s+/', '', (string) $customer?->vat_id) ?? '');
+        if ($vatId === '') {
+            return new self($domestic, false);
+        }
+
+        // A VAT ID starts with its country's code. Same country as ours means a
+        // domestic business sale, which is taxed normally.
+        $sellerCountry = strtoupper((string) config('provisioning.tax.seller_country', 'AT'));
+        $customerCountry = substr($vatId, 0, 2);
+
+        return $customerCountry !== '' && $customerCountry !== $sellerCountry
+            ? new self(0.0, true)
+            : new self($domestic, false);
+    }
+
+    public function grossCents(int $netCents): int
+    {
+        return (int) round($netCents * (1 + $this->rate));
+    }
+
+    public function percentLabel(): string
+    {
+        return rtrim(rtrim(number_format($this->rate * 100, 1, ',', '.'), '0'), ',');
+    }
+}

config/provisioning.php

@@ -107,6 +107,9 @@ return [
     */
     'tax' => [
         'rate_percent' => (float) env('CLUPILOT_TAX_PERCENT', 20),
+        // Ours. A customer whose VAT ID belongs to another EU country is billed
+        // under reverse charge — see App\Services\Billing\TaxTreatment.
+        'seller_country' => env('CLUPILOT_TAX_COUNTRY', 'AT'),
     ],
 
     // Extra storage add-on (per unit) and the add-on catalogue (labels in lang/*/billing.php).

lang/de/billing.php

@@ -1,10 +1,12 @@
 <?php
 
 return [
+    'net_reverse_charge' => 'netto — Reverse Charge',
     'net_per_month' => 'netto pro Monat',
     'net_once' => 'netto, einmalig',
     'net_hint' => 'netto, zzgl. :percent % USt.',
     'cart' => [
+        'reverse_charge' => 'Steuerschuldnerschaft des Leistungsempfängers (Reverse Charge)',
         'net' => 'netto',
         'per_month' => 'pro Monat',
         'once' => 'einmalig',

lang/en/billing.php

@@ -1,10 +1,12 @@
 <?php
 
 return [
+    'net_reverse_charge' => 'net — reverse charge',
     'net_per_month' => 'net per month',
     'net_once' => 'net, one-off',
     'net_hint' => 'net, plus :percent % VAT',
     'cart' => [
+        'reverse_charge' => 'Reverse charge — VAT payable by the recipient',
         'net' => 'net',
         'per_month' => 'per month',
         'once' => 'one-off',

resources/views/livewire/billing.blade.php

@@ -82,7 +82,11 @@
                     <span class="font-mono">{{ $eur($net) }}</span>
                 </div>
                 <div class="flex items-center justify-between text-muted">
-                    <span>{{ __('billing.cart.vat', ['percent' => rtrim(rtrim(number_format(config('provisioning.tax.rate_percent', 0), 1, ',', '.'), '0'), ',')]) }}</span>
+                    <span>
+                        {{ $tax->reverseCharge
+                            ? __('billing.cart.reverse_charge')
+                            : __('billing.cart.vat', ['percent' => $tax->percentLabel()]) }}
+                    </span>
                     <span class="font-mono">{{ $eur($gross - $net) }}</span>
                 </div>
                 <div class="flex items-center justify-between border-t border-line pt-1.5 font-semibold text-ink">
@@ -122,7 +126,11 @@
                             @endforeach
                         </ul>
                         <p class="mt-4 text-xl font-semibold text-ink">{{ $eur($p['price_cents']) }}<span class="text-sm font-normal text-muted"> / {{ __('billing.month_short') }}</span></p>
-                        <p class="text-xs text-faint">{{ __('billing.net_hint', ['percent' => rtrim(rtrim(number_format(config('provisioning.tax.rate_percent', 0), 1, ',', '.'), '0'), ',')]) }}</p>
+                        <p class="text-xs text-faint">
+                            {{ $tax->reverseCharge
+                                ? __('billing.net_reverse_charge')
+                                : __('billing.net_hint', ['percent' => $tax->percentLabel()]) }}
+                        </p>
                         <x-ui.button variant="primary" size="sm" class="mt-4 w-full" wire:click="purchase('upgrade', '{{ $key }}')" wire:target="purchase('upgrade', '{{ $key }}')" wire:loading.attr="disabled">
                             {{ __('billing.upgrade_cta') }}
                         </x-ui.button>
@@ -178,7 +186,11 @@
                 </div>
                 <p class="mt-2 flex-1 text-sm text-muted">{{ __('billing.addon.'.$key.'.desc') }}</p>
                 <p class="mt-3 text-lg font-semibold text-ink">{{ $eur($addon['price_cents']) }}<span class="text-sm font-normal text-muted"> / {{ __('billing.month_short') }}</span></p>
-                        <p class="text-xs text-faint">{{ __('billing.net_hint', ['percent' => rtrim(rtrim(number_format(config('provisioning.tax.rate_percent', 0), 1, ',', '.'), '0'), ',')]) }}</p>
+                        <p class="text-xs text-faint">
+                            {{ $tax->reverseCharge
+                                ? __('billing.net_reverse_charge')
+                                : __('billing.net_hint', ['percent' => $tax->percentLabel()]) }}
+                        </p>
                 <x-ui.button variant="secondary" size="sm" class="mt-3 w-full" wire:click="purchase('addon', '{{ $key }}')" wire:target="purchase('addon', '{{ $key }}')" wire:loading.attr="disabled">
                     {{ __('billing.addon_cta') }}
                 </x-ui.button>

tests/Feature/CartTest.php

@@ -149,3 +149,37 @@ it('keeps the recurring figure consistent with the total to the cent', function
         ->assertSee($expected)                                                     // total gross
         ->assertSee(__('billing.cart.recurring_note', ['amount' => $expected]));   // and the note
 });
+
+it('does not charge Austrian VAT to an EU business with a VAT ID', function () {
+    config()->set('provisioning.tax.rate_percent', 20);
+    config()->set('provisioning.tax.seller_country', 'AT');
+
+    [$customer, $user] = cartCustomer();
+    $customer->update(['vat_id' => 'DE 811 907 980']);
+    Order::factory()->for($customer)->create(['type' => 'storage', 'amount_cents' => 1000, 'status' => 'pending']);
+
+    // Reverse charge: we invoice net, the customer accounts for the VAT.
+    Livewire\Livewire::actingAs($user)->test(Billing::class)
+        ->assertSee(__('billing.cart.reverse_charge'))
+        ->assertDontSee(__('billing.cart.vat', ['percent' => '20']));
+
+    expect(Order::query()->first()->grossCents())->toBe(1000);
+});
+
+it('charges domestic VAT to a domestic business and to private customers', function () {
+    config()->set('provisioning.tax.rate_percent', 20);
+    config()->set('provisioning.tax.seller_country', 'AT');
+
+    [$customer, $user] = cartCustomer();
+    Order::factory()->for($customer)->create(['type' => 'storage', 'amount_cents' => 1000, 'status' => 'pending']);
+
+    // No VAT ID at all → domestic rate.
+    expect(Order::query()->first()->grossCents())->toBe(1200);
+
+    // An Austrian VAT ID is a domestic business sale, taxed normally.
+    $customer->update(['vat_id' => 'ATU12345678']);
+    expect(Order::query()->first()->fresh()->grossCents())->toBe(1200);
+
+    Livewire\Livewire::actingAs($user)->test(Billing::class)
+        ->assertSee(__('billing.cart.vat', ['percent' => '20']));
+});