SAP Note 15669 - Changability of posting date during goods movements

Symptom:

When you enter a goods movement (goods receipt, goods issue, transfer posting), the posting date is recorded. This posting date can then no longer be changed.

Cause and prerequisites

Based on the posting date, the system determines whether the goods movement is to be posted to the current period or the previous period. When goods movements are entered, the stock changes are internally checked and updated internally against the corresponding period fields of the material master. A subsequent change of the posting date would therefore require development of an incredibly complicated (and minimally useful) subroutine.

Solution
When necessary, please cancel the entry transaction (using F12 or F15) and re-enter the goods movement with the appropriate posting date.