Hello @dsimmerly,

You can change the settings of a financial period if you did not post any transactions to the period you need to modify.

Here is the Help article:

https://help.acumatica.com/(W(4))/Help?ScreenId=ShowWiki&pageid=cd9585bb-1334-4c97-8cbd-7dc22d234772

After financial periods are defined, the same periods will be used for all subsequent financial years. If needed, you can modify the financial periods of a year on the Master Financial Calendar (GL201000) form. You can change the settings of a financial period if you did not post any transactions to the period you need to modify.

Hello @dsimmerly ,

I did a quick test in a Demo.  I’m able to select ON the User-Defined Fiscal Periods checkbox, then add the 13th period, modifying its description to “December”, and save.

However, this modification affects only the current year.  When I generated the calendar for year 2025, only 12 periods were created. 

I was able to repeat the process, adding the 13th period again to year 2025.  I don’t think this solution is ideal, to move forward with having to manually add your 13th period every year.

It may be worth your time to contact Acumatica Support to see whether they can permanently change the number of periods to 13 in a way that will automatically create 13 periods every year, as you move into the future.

Good luck,

Laura