I keep mine simple. A basic spreadsheet that has fees paid, by who, when, amount to the left and then a break down of expenses in columnes to the right. Expenses are detailed by date, who paid (power, heat, grocery store), the amount by category it's entered into come tax time. These are subtotalled by month before the next month is recorded beneath. I put all receipts into a monthly envelope labelled "DAY CARE EXPENSES - OCTOBER 2017". At the end of the year, I then just have to total the categories for each month.

Income, Then the costs which are 100% daycare - Advertising, Supplies, Insurance (day care part), Maintenance (dedicated day care rooms only), Office Supplies. Then the costs which are shared daycare and personal - power, heat, water, internet, property tax, house insurance, maintenance (things like stain for deck, paint for rooms with shared use), and so on.

I keep a 13th envelope for Car Expenses - fuel, insurance, maintenance, parking fees, plate registration, MVI.

I never claim anything which I don't have a receipt in the envelope to prove.

Each year, when my husband do tax returns, he has a file that contain all 13 envelopes with receipts, power bills, Property tax bill, insurance certificate with costs, anything which proves what bills were plus the bank statements for the same 12 months showing the transactions being paid and of course deposits made that line up with client fees. He also moves into this file any tax receipts like mortgage statement showing interest paid, usual annual statement from health insurance to show premiums paid, receipts from health care costs not covered by health plan. Add in the copies of contracts from client's over the year and copies of receipts issued to all clients so that receipts given equal deposits made equal income declared.

If we get audited we know all the paper work for year in question is in that one folder. And if they questioning just one cost, we know from spreadsheet, when that cost incurred and can go directly to that month's receipt envelope to prove the expense.