What is an Earlier Year Update?
If you realise you’ve made a mistake on an RTI report in a historic tax year, for example, if you reported an employee’s pay as higher than it actually was, then you should send HMRC an EYU.
If you realise you’ve made a mistake in the current tax year, you can usually correct that on your next RTI submission. You can do this through HMRC’s Basic Tools software.
The EYU should show the difference between what you should have reported and what you actually reported. There are separate sections to show the original and revised figures.