Time is fast running out for taxpayers to avoid a £100 fine for late filing of their self-assessment returns.

The deadline for paper filing has now gone, with new taxpayers who have not yet pre-registered for online filing advised to do so immediately.

Only those already registered for online filing have enough time to complete their return online by the January 31 deadline.

Gary Richards, of Tax Assist Accountants, in Larkfield, near Maidstone, said that - unlike previous years - late filers will have to pay the penalty even if they do not owe any tax.

Taxpayers who have not filed by June face a further penalty of £10 a day, with anyone putting off the task until September out of pocket by £1,000, "an amount that is more than just irritating," added Mr Richards.

Around 5% of taxpayers - 500,000 - file online on the final day.

Mr Richards warned: "That's about 700 a minute during daylight hours - so don't be surprised if the Revenue machines start to creak a bit during the 24 hours."

However, a threatened strike by staff at HM Revenue and Customs call centres could disrupt a last-minute rush.

HMRC said it will waive the automatic £100 fine for anyone whose return was delayed by industrial action. Taxpayers must send a letter explaining the reason for the delay.