Return reason codes
A Return reason code records why a customer is returning items - quality issues, an accidental order, a change of mind - so return patterns can be analyzed later. It's purely informational: selecting one has no effect on how a return is credited or on what happens to the goods. That's the job of Disposition codes, a separate, per-line classification.
Creating a Return reason code
Navigate to Accounts receivable > Setup > Sales invoices > Returns > Return reason codes. The list opens directly in an editable state - there's no separate New form. Enter a Return reason code (a short, unique identifier, e.g. DAMAGED, SIZE_ISSUE) and a Description in the blank row at the top of the grid, then select Save.
Once saved, a Return reason code has no Edit or Delete action anywhere in the UI. If one was entered wrong, add a corrected code rather than expecting to fix the original in place, and simply stop using the old one.
Assigning a Return reason code
A Sales return's header has a Return reason field - it applies to the return as a whole, not to individual lines.