In this regulation—

• F1“the current total tax” means the amount required to be recorded at paragraph 17 of Schedule A1 (real time returns) in the most recent return which the employee is required to make in the tax year, or where the employee is required to make a return under regulation 67EA(3) (failure to make a return under regulation 67B), the amount required to be recorded at paragraph 17 of Schedule A1 for the tax year to which that return relates;

• “the previous total tax” means the total tax to date (if any) required to be recorded for the previous tax quarter in the tax year.

If, in relation to any tax quarter, the current total tax exceeds the previous total tax, the employee must pay the excess to the Inland Revenue, within 14 days after the end of the tax quarter.

... The amount payable under paragraph (2) is not to exceed the overriding limit in relation to the relevant payments which the employee has received in that tax quarter.

Any amount which is not payable because of the application of paragraph (4) must be added to the current total tax for the purpose of the calculation in paragraph (2) or (3) for the next tax quarter (if any) of that tax year.