The UK tax year for individuals starts April 6th and ends April 5th of the following year. From then, you have until January 31st to complete your online tax return for the previous tax year.

More on tax dates can be found here

Two ways:

• online or by phone: but only for the £100 late filing penalty.
• print and send the SA370 form via post

In either case, you’ll need to provide a “reasonable excuse”.

You must appeal within 30 days unless you have a serious reason for appealing late.

HMRC has over 130 phone lines, but most of them are not relevant for everyday taxpayers.

These are the most important ones:

• For questions about Self Assessment tax returns: 0300 200 3310
• For questions about how much tax you need to pay and what reliefs you can claim: 0300 200 3300
• For questions about National Insurance: 0300 200 3500

You can see all of the HMRC numbers here

Anything that stopped you from doing your taxes even if you tried to:

• your spouse or close relative died right before the deadline
• you were very sick around the deadline
• your computer failed as you were filing
• the HMRC online services didn’t work on the deadline
• a fire, flood, theft, or other major incident prevented you

But not:

• you asked someone else to do it for you, and they didn’t
• your card or payment failed
• you didn’t know how to use HMRC’s website
• you made a mistake
• you didn’t get your UTR access code in time

Yes.

If you don’t tell HMRC that you’re no longer self-employed, they’ll still expect you to file a Self Assessment tax return.

You’ll be fined if you don’t – even if you owe no tax at all.

The way you tell HMRC that you stopped being self-employed is by filing a tax return and specifying that it’s your last one.