Payroll Giving & Pensionable Pay

If someone is in a payroll giving scheme, must the pensionable pay be reduced by the amount of the charitable donation? Some sources say payroll giving is a salary sacrifice and some say it isn't but either way, can the EMPLOYEE DECIDE if they wish their pensionable earnings to be reduced by the value of the payroll giving or is the EMPLOYER REQUIRED to reduce their pensionable earnings accordingly?

Hi,
You will newed to contact our Employers team regarding this.
Employers: general enquiries
Thank you.