I often get questions about using a 13th period for year-end in GP. The extra period is usually not the real issue. Underlying the question is that folks want a way to identify and segregate specific journal entries. These could be post-period adjustments, auditor required entries, corrections, etc.
I don’t recommend a 13th period in GP. It’s not necessary and it can wreak havoc with fixed assets if you aren’t careful and cause problems with deferrals. Instead, create additional Source Documents for Journal Entries in GP. For example, one could be labeled AUDIT for audit adjustments, another could be PCLOSE or YE for post-close year-end fixes.
These entries are searchable in Smartlists making it easy to identify different types of journal entries.
A secondary benefit is improved consistency around adjustments. Most organizations don’t have some kind of extra period for quarter end adjustments, but this process can be used for any post-period adjustment making those transactions more consistent and easier to review.
Links to all the posts in this series can be found at https://dynamicaccounting.net/gp-controller-series-index/