diff --git a/app/Services/Billing/TaxTreatment.php b/app/Services/Billing/TaxTreatment.php
index ca0b9ae..3703c4f 100644
--- a/app/Services/Billing/TaxTreatment.php
+++ b/app/Services/Billing/TaxTreatment.php
@@ -3,6 +3,7 @@
 namespace App\Services\Billing;
 
 use App\Models\Customer;
+use App\Support\CompanyProfile;
 
 /**
  * Which VAT applies to a customer, and why.
@@ -37,7 +38,12 @@ final readonly class TaxTreatment
 
     public static function for(?Customer $customer): self
     {
-        $domestic = (float) config('provisioning.tax.rate_percent', 0) / 100;
+        // From the Finance page, not from config: an operator can change the
+        // rate there and cannot change a config value, and two sources for one
+        // number is how an invoice ends up disagreeing with the checkout that
+        // produced it. CompanyProfile falls back to the config value until a
+        // rate has been saved.
+        $domestic = CompanyProfile::taxRate() / 100;
 
         // Unverified is the normal state, and it must cost the customer nothing
         // more than the domestic rate they would pay anyway — but it must not
diff --git a/app/Support/CompanyProfile.php b/app/Support/CompanyProfile.php
index 3cf12ee..710812a 100644
--- a/app/Support/CompanyProfile.php
+++ b/app/Support/CompanyProfile.php
@@ -95,9 +95,20 @@ final class CompanyProfile
         ));
     }
 
-    /** The VAT rate as a percentage, e.g. 20.0. */
+    /**
+     * The domestic VAT rate as a percentage, e.g. 20.0.
+     *
+     * The ONE place it is decided. App\Services\Billing\TaxTreatment reads it
+     * from here rather than from config, because this page can change it and a
+     * config value cannot — and two sources for one number is how an invoice
+     * ends up disagreeing with the checkout that produced it.
+     *
+     * Falls back to the .env-derived config until an operator has saved a rate,
+     * so an installation that already carries CLUPILOT_TAX_PERCENT keeps
+     * working unchanged. Same shape as App\Support\ProvisioningSettings.
+     */
     public static function taxRate(): float
     {
-        return (float) Settings::get('company.tax_rate', 20.0);
+        return (float) Settings::get('company.tax_rate', (float) config('provisioning.tax.rate_percent', 20));
     }
 }
diff --git a/tests/Feature/Billing/FinanceSettingsTest.php b/tests/Feature/Billing/FinanceSettingsTest.php
index badef37..fb5c274 100644
--- a/tests/Feature/Billing/FinanceSettingsTest.php
+++ b/tests/Feature/Billing/FinanceSettingsTest.php
@@ -132,3 +132,18 @@ function issueOne(InvoiceSeries $series): Invoice
         'currency' => 'EUR',
     ]);
 }
+
+it('decides VAT in one place, so the invoice cannot disagree with the checkout', function () {
+    // Two sources for one number is how a document ends up contradicting the
+    // page that produced it. The Finance tab is the source; config is only the
+    // fallback until a rate has been saved.
+    config(['provisioning.tax.rate_percent' => 20]);
+
+    expect(App\Support\CompanyProfile::taxRate())->toBe(20.0)
+        ->and(App\Services\Billing\TaxTreatment::for(null)->rate)->toBe(0.2);
+
+    App\Support\Settings::set('company.tax_rate', 10.0);
+
+    expect(App\Support\CompanyProfile::taxRate())->toBe(10.0)
+        ->and(App\Services\Billing\TaxTreatment::for(null)->rate)->toBe(0.1);
+});