HM Revenue & Customs (HMRC) have recently checked tax
calculations and found that some people have paid the wrong amount
of tax. If this applies to any of your employees, they will receive
a letter from HMRC and a form P800 Tax Calculation. This shows the
recalculated tax amount and indicates whether they have paid too
much or too little tax.
For more information about the form P800 Tax Calculation and
what you need to do in your payroll software, please refer to Ask
Sage article
26419.
HMRC have also provided detailed information for employees on
their website.