The plugin ensures that customers always pay the correct amount in base currency, regardless of which currency the invoice is displayed in. Invoice Creation: Invoice total is saved in base currency (USD) Display: Total is converted to invoice currency for customer view using current rates Payment Time: Customer's payment is automatically converted back to base currency using current exchange rates Validation: System verifies that the payment in base currency equals (or exceeds) the invoice base amount Example 1: Base Currency = USD Base invoice amount: $1,000.00 USD Invoice currency selected: EUR (rate = 1.1) Display amount to customer: €909.09 ($1,000 / 1.1) Customer pays: €909.09 Conversion at payment: €909.09 × 1.1 = $1,000.00 USD ✓ Example 2: Base Currency = EUR Base invoice