To configure auto reconcile method , go to Accounting –> settings

In account settings go to customer invoice section and locate auto reconcile method

1. First in First: allocates the payment to the oldest pending invoice first.

• Invoice A: $18.00 (older invoice)
• Invoice B: $37.95 (newer invoice)
• Payment posted: $37.95

Since the method is First In First, the payment will be applied to the oldest invoice first.
Result: The payment is first applied to Invoice A ($18.00).
Remaining amount = $19.95 The remaining amount is then applied to Invoice B, making it partially paid.

Create two invoices for the same customer: Invoice A dated older date

Invoice B dated newer date

Create a payment for the same customer

The system first matched Invoice A, because it was created earlier If there is still remaining payment amount, it moves to the next invoice.

2. Same Amount: matches the payment to an invoice with exactly the same balance

When a customer payment is posted, the system looks for any invoice of that customer whose remaining balance matches the payment amount exactly. If such an invoice exists, Odoo automatically reconciles the entire payment with that invoice.

Example:

• Invoice A: $18.00
• Invoice B: $37.95
• Payment posted: $37.95

The payment will be auto-applied ONLY to Invoice B because its amount matches exactly.

3. Latest Invoice: ensures the payment is applied to the most recently created or dated invoice first.

When a payment is posted, the system sorts all pending invoices by invoice date (or creation date) from newest to oldest. The payment is then applied starting from the latest invoice and continues until the payment amount is fully consumed.

Example:

• Invoice A (older): $18.00
• Invoice B (newer): $37.95
• Payment posted: $20.00

The system will apply the $20.00 towards Invoice B first, because it is the latest invoice.