HMRC is asking for more businesses and software developers to join the PAYE Real Time Information (RTI) pilot scheme.
HRMC has already recruited 300 volunteers to test drive the system before its initial launch in April and is inviting a further 1,300 volunteers to join the test scheme in July 2012, then an additional 250,000 volunteers from November 2012.
Stephen Banyard, HMRC's acting director general for Personal Tax, said: "Expanding the pilot from the original 300 employers will help ensure the smooth implementation of RTI. It is an ambitious but achievable target as we know that RTI is on track.
"We have considered all the technical and practical issues and are confident that we have the capacity to increase the pilot by over 300 per cent in July next year."
Once the test programme has been completed, all employers will have to start submitting monthly PAYE returns to HMRC under RTI from October 2013 - whether or not any problems identified during testing have been sorted out.