Hi Frances Shuttlewood,
If you submtited your registration online the current timescale to allocate the UTR is 3-4 weeks.
If this timescale has passed you will need to contact HMRC to check on the progress.
Self Assessment: general enquiries.
When we issue the notice to file the 2022/23 Self Assessment as issued late you will get 3 months and a week to file the tax return before late filng penalties apply.
Thank you.