Here are the steps to add an advance payment for vendors:

1. Open the Moon Invoice application on your device or tap on this link.
2. Navigate to: Purchases > Vendors.
3. Select the vendor you wish to add an advance payment for.
4. Tap the dollar sign ($) icon to open the Payment screen.
5. Choose the payment mode, enter the advance amount, and optionally add notes.
6. Tap Save to record the payment.
7. The payment will now appear under Payment Made.
8. Now, you can edit or print the payment using the Edit and Print icons if required.