Your accountant really only needs a spreadsheet listing the donations or a total dollar amount, unless they are being a pain in the butt.
However, by law you are required to have, for any donation amount no matter how small, an electronic or bank record such as a canceled check or credit card statement. And the church is required by law to issue either individual receipts, or an annual statement, if any individual gift or your total of annual gifts is more than $250. This is a big deal so I would be very surprised if the church does not do this and I would wonder what else they are doing wrong with their money that might be less obvious. If you don't have these proofs, you will lose the deduction if you are audited.
However, as a practical matter, this means that if you prefer to donate by placing loose cash in the collection plate anonymously, you can't deduct it from your income tax.
