If I am late in filing a Self-assessment What steps should I take

I did not aware I need to file a self- assessment due to mistaken of the law. And I just learned that the deadline for online filing was 31.1.2023 at the weekend right before it by coincidence (from a U-tuber). As I am still awaiting my NI to be posted to me in the next 3 weeks. And I just learned how to apply for an UTR by post today (instead by online application that I had kept on trying many times but failed since last week). IF there will be a PENALT Y imposed, what should I do first? Should I send in my SA100, SA106 and SA109 in a paper form by POST as soon as possible ?? OR should I wait till I get my UTR then submit online ?? Look forward for your kind reply. stevesung

Hi,
 

If you have not yet been registered, you will be given 3 months and 7 days to file the return without incurring a late filing penalty. The original payment date of 31/01/2023 will still apply . Thank you.