I don't think anyone would support that, but that's not what happens -- you can see the breakdown of gross/net salary & taxes on every payslip you receive from

I don't think anyone would support that, but that's not what happens -- you can see the breakdown of gross/net salary & taxes on every payslip you receive from your employer, as well as on your annual P60 https://www.gov.uk/paye-forms-p45-p60-p11d/p60 https://www.gov.uk/paye-forms-p45-p60-p11d/p60