Fiscal date of study

Hello everyone,

I have started a 27-credit course, which means I retain my status as a self-employed student. I started this course in 2025 and it runs until June 2026. I started my business at the beginning of October, and in November and December I was well below the social security contribution exemption threshold. To date, I have not entered my study costs. I would like to enter them in the 2026 financial year, as this would suit me very well. Can I set the fiscal date of my study invoice to 2026 (e.g. January), regardless of the fact that the invoice date is the end of September 2025?

Thank you in advance for your help!

Regards, Melih