The self-employed and those with more than one source of income must submit their self-assessment forms online by 31 January,
Data from returns made last year showed that men were most likely to file late.
Those aged between 18 and 20 and living in London were the worst offenders, the tax authority said.
So far, 6.45 million returns have been submitted ahead of the deadline at the end of the month, with about another 4.5 million outstanding.
"Whatever your gender, age, occupation or location, if you haven't sent in your 2013-14 tax return, you need to take action now. Don't leave it until the last minute to contact us. Do it now, and avoid a last-minute rush to beat the deadline," said Ruth Owen of HM Revenue and Customs.
The figures from a year ago showed that the over-65s were the most punctual.
Interestingly, lawyers and accountants were not the most punctual - with 219 late filers per 10,000 submitted. Those in agriculture, fishing and forestry were more efficient, with 109 per 10,000 filing late.

Yeovil District Hospital was put on "black alert" last year when it was overwhelmed by demand.
This year the hospital is installing a 24-bed modular ward on its roof and leasing 18 beds from a nursing home.
Chief Executive Paul Mears said: "Winter is a challenging time for us and we've taken action to ensure we're well prepared for this winter."
Last February, the hospital was put on "black alert" for two weeks as it struggled to cope with the number of people coming into its accident and emergency department.
What is a black alert?
â€¢The NHS uses a national internal alert system based on the colours green, amber, red and black to rank how busy a local health and social care system is
â€¢Black alert status occurs when a hospital cannot cope with the number of people coming into the accident and emergency department because not enough people are being discharged
â€¢It effectively means the hospital does not have enough bed capacity to cope
This year, to boost bed capacity, the hospital is hoisting a permanent emergency admissions unit onto the roof of its outpatient department in the run-up to Christmas.
It has also contracted with a local nursing home to take 18 beds for six months for patients waiting for nursing home placements or a package of care.
"Last winter was really, really bad for us - part of that was due to the complexity of the patients we were admitting which were a more elderly, frail group of patients and also the sheer numbers," said Mr Mears.
"But we've got 42 beds on top of our current bed base now and we believe that will put us in a much better place to be able to cope with the additional pressures."

Children's services in the city have consistently been rated "inadequate" by Ofsted.
Lord Warner was appointed as an independent commissioner last year to oversee attempted improvements.
On Monday the council's cabinet approved plans that will see an extra Â£94m spent over three years.
It includes Â£27.5m already announced for the 2015-16 financial year.
New IT and upgrades to existing systems are also to be introduced, including mobile devices for all social workers.
Under the plans, the number of front-line social worker posts will increase from 511 to almost 600 by March 2017.
The authority has struggled to recruit enough social workers over recent years, particularly those with substantial experience.
Councillor Brigid Jones, in charge of children's services, said the authority had previously relied on "emergency measures" to tackle staff shortages and the latest plan allowed it to approach the matter more "more strategically".
"The biggest thing we need to get right is the recruitment. It's about getting the right staff here and keeping them," she said.
Lord Warner is expected to publish his own report into the state of children's services in Birmingham next month.
Young men working in the communications industry are the most likely to miss the looming tax return deadline, HM Revenue and Customs figures suggest.
[NEXT_CONCEPT]
A "ready made" ward is to be craned onto the roof of a Somerset hospital to help cope with winter demand.
[NEXT_CONCEPT]
Extra social workers and new IT systems are to be introduced in a bid to improve children's social care in Birmingham.