Does the IRS accept written receipts that are being claimed as a business deduction?

I've gotten a correspondence audit letter and the IRS is requesting documents supporting a business expense for $5400 that I claim on a schedule C.  I purchased the items from a local seller and he provided me with a written receipt with the items bought and the amounts paid.  Will the IRS accept a written receipt?  Does the receipt need to contain specific information? Name of the store, phone number? Etc.