One third of the expected self-assessment tax returns for 2016-2017 are still outstanding with only one week to go before the 31 January deadline.
According to HMRC, some eight million people have filed their self-assessment tax returns for 2016-17. That leaves some three million tax-payers that yet have to complete their online form.
HMRC is reminding customers that anyone that files their return late will receive a £100 penalty - even if they do not owe any tax. And the longer they delay, the more they will have to pay.
Angela MacDonald, HMRC director general of customer services, said: "The seven-day countdown to 31 January has now begun. Put a stop to that niggling feeling and do your self-assessment now. Our helpful online services offers support and advice so you can complete your tax return quicker than you think."
The deadline for sending 2016-17 self-assessment tax returns to HMRC, and paying any tax owed, is 31 January 2018. Self-assessment customers can now also submit their return via their personal tax account.
Anyone submitting their 2016-17 self-assessment return online for the first time will need to register for SA Online on the Government website. It can take a few days for the registration to arrive in the post so HMRC is warning that customers need to do this as soon as possible.
HMRC is urging anyone that is worried about meeting the deadline to get in touch via the self-assessment helpline (0300 200 3310).
There are guides and tools to help you with self-assessment on Money Donut.