What if I cannot pay my tax bill?

File the return on time regardless. The penalty for filing late is separate from the penalty for paying late, and there is no reason to collect both.

Then contact HMRC about Time to Pay. For most Self Assessment bills under a certain amount you can set the plan up online through your HMRC account without speaking to anybody, spreading the bill over monthly instalments.

Interest still accrues on what is outstanding. But if the arrangement is in place before the late-payment penalty dates, the penalties themselves can usually be avoided.

The thing that makes this go badly is silence. HMRC is markedly more accommodating with somebody who rings before the deadline than with somebody they have had to chase.

The longer-term fix is putting money aside as you go. JoltMile estimates your bill as the year runs so the January figure is not a surprise.