If you have a Partnership or an S-Corp that uses a calendar year, the due date for a timely filed return for tax year 2024 is March 17, 2025. This has nothing to do with self-employment taxes.
Self-employment estimated quarterly taxes are due the year before on the following dates: April 15, June 15, September 15 and January 15 of the current year. The estimated quarterly tax payment due on April 15, 2025 corresponds to next year.
I’m still confused. I was working as a private contractor for three months at the end of 2024 so when are my taxes due?
It depends. Tax returns for the entities provided by @NicolleR1 do have a different tax filing deadline than individual tax returns.
If you are stating that you are a sole proprietor, then you file a regular individual tax return due on April 15, 2025.
If you are filing as a C-Corporation then the due date is April 15, 2025.