HMRC has published guidance on auto-coding for tax agents preparing returns during Self Assessment season.
With auto-coding, the Revenue can automatically update a customer's PAYE tax code with information from their SA return.
It was introduced for 2010-11 tax returns and is a quicker way of correcting tax codes to ensure clients pay the right amount of tax, according to HMRC.
Auto-coding uses information of other income and deductions from the return to calculate and issue a revised tax code for the current year.
Sending tax returns earlier will ensure that HMRC uses the right tax code, they stressed.