Hello Ehill2766-gmail-
Welcome to the Community page,
So the year runs April to April but it will depend on who you file it, whether you are doing it online filing or paper, if you are unsure then you will need to ring and speak to HMRC and they will advise what kind of filing you need to do and when you need to file your return for.
If you have a look at this link it tells you more about it as well. it also tells you the dates of both the paper and online when need filing if you unsure which one you need to do speak to HMRC.