HMRC not only had to deal with the biggest shakeup to PAYE since it was first introduced over the weekend, but had to do so at the same time as an unavoidable IT reboot, it has been revealed.

RTI came into full-force on Saturday, meaning a number of employers attempting to report employee pay information onto the HMRC system for the first time had to do so as the same system was being updated with the tax changes brought about due to the arrival of the new tax year.

The IT update was completed early on Saturday and according to an HMRC spokesperson, a few early-bird users were subject to 'some minor delays as the system was bedding in'.

HMRC was quick to stress that the system was running as expected 'by lunch time' and as of today (9 April) more than 70,000 returns using RTI had been successfully submitted.

Ruth Owen, HMRC director general personal tax, said: 'We are under no illusions - we know that it will take time before every employer in the country is using RTI. We appreciate that some employers might be daunted by the change - but they don't need to be. HMRC is on hand to offer help and support and we are taking a pragmatic approach - which includes no in-year late filing penalties for the first year.'

The intention is that RTI will improve the operation of PAYE for employers, HMRC and employees - although businesses with less than 50 employees are not required to report in real time until 6 October 2013.

For more information and help on RTI, go to HMRC.