Basic RTI CATEGORY LETTER C

I have an employee who will be at pensionable age ( 66 ) shortly but intends to carry on working, in RTI do I just change the cat. Letter to C ? I am confused by advice to " Carry on reporting year to date information under the old category letter until the end of tax year." I cannot see how you could do this. Help please. ,

Hi,
 

When someone reaches state pension age you should use NIC table letter C from the first pay day after the employee reaches State Pension age. Keep a copy of the proof of employee's date of birth for their own records. Update the employee's NIC letter on their payroll software from the date it should be used. Make sure this is shown on the next Full Payment Submission (FPS). Include the current year to date figures for each correct NIC table letter  . Thank you.