HMRC broke through the three million self assessment returns filed online on 27 January, said an HMRC press spokesman, with 3,067,306 returns having been filed online.
He added that the service is coping well with this unprecedented number of returns.
HMRC say that about 75% of the returns being filed online are being submitted by tax advisers.
They have also said that the percentage of self-assessment online returns with attachments stands at 2.6%.