IMO aside from keeping all the receipts separate which is also a PITA there is no hard and fast way to do this that does not include some sort of 'mathematical equation' - basically you can write off any 'reasonable' expense for business as long as you have the receipts to back it up and feel you can argue in an audit it was 'reasonable' and win ... and sadly some big business employ lawyers full time arguing with CRA around the definition of reasonable tax write offs so it is not so black and white in any industry you might work in .... everyone hates tax time

Do you know how much you spent on average per week BEFORE you opened the daycare cause that would be very helpful?

Have you kept ALL your receipts for groceries to prove that you fed your family as well as the daycare children?

Because the easiest way to determine how much is 'daycare related' is that if you know before daycare you spent an average of $150 a week on groceries and now with daycare you are spending $230 a week that means that on average $80 a week daycare related and the rest is family ... so you could just multiple $80 a week by the number of weeks you ran your daycare this year ... and be done with your math if you are happy with an 'average' amount

If you want to figure out how much per child and you have had 3 children on enrollment on average each day that means you are spending $5/day/child on food ... so some days you might spend more and some days less but 'on average' is reasonable.

IMO as long as you have 'receipts and reasonable math' to show why you claimed the way you did and can argue it was reasonable ... aka that you spent X on daycare to feed this many children and you spent Y on your own personal groceries to feed this many adults and children to prove your own family ate a financial equivalent lifestyle to the daycare children ... aka they ate same quality or better meals than the daycare children did you should be fine in an audit!

My understanding is that providers who've gotten into trouble in an audit over food did so because they A) did not have a reasonable argument as to why the chose the amount they did it was just an 'arbitrary number they had heard from other providers' or B) they did not ensure they had the receipts to back up the amount they claimed ... so for example you often hear people stating that they write off as high as $10/child/day for their equation which could very well be if they are eating really high quality meats, organic fruits/veggies and have hearty eaters in their group .... however it get away with writing that off that means that assuming they have 5 children all year long and only take two weeks vacation that they better have at least $12,000 in grocery receipts for the daycare AND they better be able to prove that they fed their family SAME OR BETTER so if they are a family of 4 themselves than they better have at least $14,600 in additional grocery receipts and that would assuming their family only at two snacks and a lunch typically served in daycare ... if they are eating breakfast and suppers as well you'd have to have my guess TWICE that in receipts to prove that the families 'expenses' were not mixed up in the daycare equation .... so you are looking at having over $30,000 in 'grocery receipts' to be able to reasonably back up that math in an audit ... and if you DON'T have receipts like that than time to reconsider the math