The Revenue Commissioners have announced an extension of the 2018 Pay and File deadline.
The deadline has been moved to 6.00pm on Wednesday November 13th.
Revenue says that with taxpayers and agents working towards a deadline of midnight on Tuesday, its Revenue Online Services (ROS) system has been experiencing very heavy usage volumes.
It says up to 4,000 returns were filed per hour throughout Tuesday morning.
These volumes caused intermittent downtime for some of those using the ROS system.
While it was still possible to file returns, Revenue says the volume of submissions were less than expected.
Revenue's technical team fully refreshed the system, which resulted in the ROS system being unavailable for a period of time.
The system is back in operation and being kept under "constant review."
Revenue has apologised for any inconvenience caused.