If you need to submit a tax return by 31 January 2017, then you need a Unique Taxpayer Reference in order to do this. This is a 10 digit number in the format 12345 67890. It takes a week to 10 days to get a UTR issued, and if you have done nothing yet, then you are unlikely to make the deadline. The penalty is 100 pounds.
Basically the 100 pounds is now a writeoff. The next deadline to seriously worry about is 2 March 2017, when an additional charge of 5% of any income tax still outstanding will be levied. There is enough time between now and then to get you registered for Self Assessment, get the tax return filed and the tax liability paid. We can do it all-electronically at our end, and we can do it quickly because we aim to be the local accountants Carlisle businesses can turn to when something needs to be done in a hurry.