charging for school runs/school hols

[Cwmbranchildminder]

Help/advice on charging

Im having 2sibling for 2.5hrs everyday after school then every school hols for 7.5hrs.
Mum wants to pay monthly(1st of every mth) how do I work it out for one as everymonth has different numbers of days!
Also some months there will be school hols?

Im a tad confussed, mum is fine however I work it out.
When she was here she signed contracts for the after school and she said charge the hrly rate x 365 and divide by 12 but after thinking I over charged. Since spoken and suggested I worked out every hols/school weeks and dividing it equally so every month is the same.
Now I got the dilema of finding out school hols/how many and dates
What would you lot do?Am I right doing it this way!
I'd prefer to be paid weekly as it would make it easier but she said she'd rather monthly
Sorry post so long! Help appreciated

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lol - id very much appriciate that!
Thank you very much! What would I do with out Mumsnet!
My email address is [email protected]

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SHOSHA -

Received with loads of thanks!
Great help

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I've got some on monthly invoices who pay exactly what they've used. I've got 2 parents who pay 12 equal payments -
39 termtime weeks + 13 school hols / 12
Any additional days/hours/meals are paid for separately when booked. xmas & easter are paid 1/2 fees. If I have to close/take additional holiday I will refund. I'm doing a statement every term so we can keep track and review.

Much prefer doing the monthly invoices though.