The paper filing deadline is 31/10/2023 and 31/01/2024 for online.
The online return is processed straight away and the paper return needs to be processed by HMRC.
If you file online you can see any amount you owe or are due as a refund straight away.
If you wish to complete a paper return you will need to contact the Self Assessment helpline and advise which pages you require for the return.
Self Assessment: general enquiries