Can I deduct a bad check on my business expense?

If you are on a cash basis, you do not deduct a bad check as a business expense. As the bad check was not paid, it is not included in your income and you cannot deduct it as an expense. In fact it is already deducted from your income by not being paid.

But if you do include it in income you can deduct it as a misc other expense.  It will be a wash.