Estimated earnings FY23/24

Coming back to the discussion on estimated earnings for FY23 and how to calculated this as I have had issues with HMRC incorrectly adjusting this as an annual bonus is paid in in May and this has in certain years resulted in HMRC incorrectly adjusting my annual estimate earnings. For illustration purposes what should be included Base Salary + guaranteed benefits (car allowance)? Deductions, I make 17% pension contributions under salary sacrifice all done through PAYE through my employer. Can I still claim additional tax relief over and above the 20% by either adjusting the allowance/ deduction or can this only be done via self assessment?

Hi
It is your decision if you would include the bonus in the estimate.
Pension contributions taken before tax would not be eligible for tax relief.
They are only eligible on contributions taken after tax.
Thankyou.