One off pension contribution calculation for tax dummies

Can I please clarify a simple scenario. If in a year someone has already earned 109,999 as PAYE income and wishes to preserve the full tax free allowance, how much would they need to contribute to a private pension before tax year end to affectively earn £99,999 for the year? Is it £8,000 or £6,000? I assume the former, as the additional relief is claimed back from self assessment. Is that correct?

Hi,

If you are based outside Scotland and you pay £6,000 into your pension from your net wage the grossed up figure woud be £7,500. If £8,000 the grossed up figure would be £10,000.

Thank you.