Taxpayers are being reminded to submit their self-assessment forms, with 100 days to go before the online deadline of January 31.
HM Revenue and Customs (HMRC) said people can avoid the stress of the Christmas and new year rush by getting their returns in early.
Last year more than 2,000 people sent HMRC their tax returns on Christmas Day.
The deadline for paper tax returns is October 31 and the cut-off for online returns and paying any tax owed is January 31.
If people miss the deadline, they can face a minimum £100 penalty for late submissions.
Angela MacDonald, HMRC’s director general for customer services, said: “The deadline for completing self-assessment tax returns is only 100 days away, yet so many of us wait until January to start the process.
“Avoid the last-minute rush by completing your tax returns on time and then enjoy the upcoming festive period.
“We want to help people get their tax returns right – starting the process early and giving yourself time to gather all the information you need will help avoid that stressful, late rush to file.”
Tax is automatically deducted from the majority of UK taxpayers’ wages, pensions or savings.
But some people have to fill in a self-assessment return each year, such as those who are self-employed or who are liable for the high-income child benefit charge (HICBC).
People with incomes over £50,000 who receive child benefit, or those whose partner gets it, are liable for the charge.
Self-assessment guidance is available at www.gov.uk/self-assessment-tax-returns.