Hi,

1 - Go to Accounting → Accounting → Reconciliation

                   - You'll land in the reconciliation dashboard.

 2- Search for the Customer

                     - Find the partially paid invoice.

                     - It will show the remaining balance on the right side.

3- Click “Reconcile”

                     - You’ll see options to match the residual amount.

4- Click “Add a Write-Off”

                     - Enter a reason (e.g., "Small balance write-off").

                     - Choose the write-off account (e.g., Bad Debt, Rounding Differences, or a custom Write-Off account).

                     - Confirm.

5- Done. The invoice is now fully paid with the balance written off.

Refer to the following solved forum for more information.

-https://www.odoo.com/sl_SI/forum/pomoc-1/how-to-write-off-uncollectible-accounts-receivable-in-odoo-17-258249

- https://www.odoo.com/sl_SI/forum/pomoc-1/what-would-be-the-best-way-to-write-off-a-receivable-147723

Hope it helps.