More than half of all those who filed their tax returns on time this year used the Revenue Commissioners' new online service (ROS).
Revenue said that by midnight last night, some 157,218 income tax returns were filed using the system. Those who file online may file up to three weeks after the usual October 31st deadline for submitting the returns manually.
According to Revenue, early indications suggest that over 50 per cent of "timely filers" used the electronic system this year, compared with 40 per cent last year and just 9 per cent in 2002.
"There were no problems with the performance of the system this year despite the heavy traffic," Revenue said in a statement.
"During the year Revenue undertook major enhancements to the service to make sure there would be no problems. The co-operation of the tax practitioners and the fact that many customers are now very familiar with the ROS system also helped enormously to ensure a successful and smooth operation."
The ROS helpdesk, which remained open until after midnight, reported a very busy day right up to the deadline, in order to help resolve difficulties for last-minute customers to file returns and make payments, Revenue said.
A total of 18,600 returns were filed yesterday alone.
Revenue said that in terms of overall compliance levels, early indications suggest that the level of timely compliance by taxpayers (using both paper and electronic methods) is up again this year.