Rather than report benefits on a P11D at the end of the year, you can instead use Payrolling of Benefits (PBIK).
You must have registered with HMRC to do this before the start of the tax year.
When you record a benefit set the Declaration Type to 'PAYE'.
Now whenever you pay the employee an additional line will appear on the on-screen payslip showing the value of the Benefit.
Tax will be calculated on pay as usual, with the addition of the value of the benefit.
Whilst the benefit increases the taxable pay, it doesn't add anything to the take-home pay of the employee and isn't visible on the payslip PDF.