Forgot to enter a sales invoice in 2023

I would advise against reopening quarters unless you know exactly what you are doing. That invoice will no longer be included in your vAT declaration by Dexxter. There are three options. 1. Reopen the quarter, delete the invoice and reissue it in the current quarter. 2. Manual attach the invoice to the next quarter when you submit your return to Intervat(this is the most correct way, but also the most difficult). 3. Leave everything as it is because it is a small amount. Hopefully, the auditor will not notice this. In any case, print your diaries and note what you did on a post-it note or something similar next to the invoice in question, so you will remember later.

Thank you very much for this comprehensive answer. I can now get to work.