Hi Lucie,
I would like to bring to your attention a discussion I have started :Special Periods - Year-end adjustment. Please see the answer of Thomas. I think it might help you.
If your customer has a fiscal year of 12 periods, you don't have to create another fiscal year in the business configuration "other fiscal year". You need to use the closing step to identify the entries of the auditor.You can then use the closing step filter in different reports. You can also create your own closing steps to identify, for example, what's should be in period 13 and 14.
Hope this helps!
Thank you,
Andréannr