45% of tax returns remain outstanding with a few weeks to go until the online filing deadline on Sunday January 31st.
A total of 12.1 million notices to file a tax return were sent out by HMRC, with a requirement to report the income period April 2019 to April 2020.
The paper deadline passed by last October, with 450,000 tax returns sent to HMRC via post.
6.6 million tax returns have been filed online so far and 5.4 million are yet to filed online before the end of January deadline.
Near 3,000 tax returns were filed on Christmas Day, and even New Year's Day saw an influx of completed tax returns, with around 18,000 submissions.
HMRC are urging people to get started as soon as possible as filing their tax return may take longer than anticipated with research by 'Which?' showing the average tax return takes 3.5 hours to complete.
Due to the circumstances surrounding the pandemic HMRC have provided the facility to spread tax bill payments using a 'Time to Pay' payment plan (for bills up to £30,000) - however larger bills may be considered by contacting HMRC directly.
The appeals period for late submissions has been extended to 90 days too, so if a reasonable excuse is provided for a late tax return or payment, the automatic penalty could be reversed.