Payment to employer’s pension scheme

Hi, I am a high rate tax payer with annual salary being more than £100,000 (for example £103.000). I pay £3600 into my employer’s pension scheme and this amount is deducted from salary after tax and NIC. In the pension statement, there is one line called “The government added: £900”, which I understand is the basic rate relief. I think I can claim the higher rate relief through self- assessment. However I am not sure what number I should put in the self-assessment form. Should I put in Box 1 - Payments to registered pension schemes operating as “relief at source” the amount of £3600+£900 = £4500. Or should I put in Box 3. - Payments to your employer’s pension scheme which were not deducted from your pay before tax, the amount of £3600 only? Can I use the pension contribution in calculating adjusted net income for 30-hour free childcare? If yes, which number should I use? The £3600 contribution + £900 tax relief or just the £3600 contribution only? Thank you

Hi tnguyen129,
It will be box one you would enter the figure including the basic rate relief.
Yes, you can include the pension contribution for the adjusted net income
Please see guidance here:
Personal Allowances: adjusted net income
Thank you.