Spreadsheets can be quick to learn, simple to use, and a real boon in keeping track of your expenses. BUT, they are not the same as a Profit & Loss (P&L) statement for income tax purposes.
I am happy when a client sends me a spread sheet for the business expenses, as I know they did a good job of record keeping. However, most often, they are a projection of cash flow, or sometimes, budgeting. These are vastly different purposes that determining profitability.
As an example, I received a spread sheet for a real estate rental which had all the expenses neatly categorized on a monthly basis, right down to the travel expenses, mileage, mortgage payments, furniture payments, etc. The only trouble with this system is travel expenses were deductible only to the extent of business mileage used during the year, which turned out to be 18+%, and of course, my client listed 100% of all car related expenses. The mortgage payments are deductible to the extent of mortgage interest allowable, not 100% of the payments made, and I found furnishings listed twice; once under the amount paid for furniture, and again as payments on the loan.
So, my client who thought he had a huge loss on the property, actually about broke even. Then, when you consider the passive activity rules, because he and his wife had Adjusted Gross Income in excess of $100,000 the phase out rules begin. Normally, as long as you qualify as an active participant in your rental properties, you can take up to a maximum of $25,000 in losses, to offset other income. But once your Adjusted Gross Income reaches the phase out limits, you can lose the ability to take any loss in the year in question.
In this case, a P & L statement would have shown them the approximate actual profit or loss on the property, rather than the cash flow expended on the rental. There are many excellent simple accounting programs available, and if you have the time and inclination, they will do a far better job of showing profitability. Your spreadsheet can still be used as a projection of cash flow if desired.