Can someone help me with a final payslip calculation?

[SandStorm]

I do the payroll for a local playgroup and a member of staff is leaving. She is paid termtime only but prorata over twelve months.

How do I calculate her final pay if she is leaving mid-December and our year runs from April-March? I'm getting very confused.

Also, her hours and hourly rate have changed over the course of the nine months. Presumable I use the final hours/wage rate in my calculation? (I'm okay with calculating the holiday).

Work out how many hours to date she has done + holiday. Use the rate at the time she was employed so have to change the rate half way through the year.

Work out how much she has been paid to now.

The difference is what she is owed.