Before the contribution:
Taxable income £125,000
Personal allowance zero
Employee National Insurance £6,464.16
Empoyer National Insureance £16,058.78
Tax £42,500
Net pension contribution zero
Income after tax £76,035.84
After the contribution:
Taxable income £100,000
Personal allowance £12,500
Employee National Insurance £5,964.16
Empoyer National Insureance £12,608.78
Tax £27,500
Employer pension contribution £28,450.00
Income after tax £66,535.84