From the total weekly food cost only 5 out of 7 days are taken into consideration for daycare. Only a portion of the food consumed during those 5 days kids are here are considered for daycare since they are not having dinner or breakfast here. Calculations are detailed in case a CRA audit. Last year it was from 36% to 45% of the total food cost for daycare, depending of the number of children under my care. I always file myself. For mortgage, services, etc I use number of rooms used divided by total number of rooms (Sq footage can also be used). Daycare areas are dedicated here. If they were shared for my personal use only a % based on the hours used for daycare should be considered.