Scrubbing accounts payable refers to the clean up of the vendor master file in your accounting software. When you scrub accounts payable, you are eliminating duplicate entries in the vendor master file, so that there are no duplicate records for the same supplier. It also means that you delete inactive suppliers from the file.
By scrubbing accounts payable, you are reducing the risk of having different records for the same supplier, each with potentially different payment terms, addresses, and so forth. It also allows you to more easily organize your record keeping for each supplier, so that you can more easily approach them about volume discounts (which would otherwise be dispersed across multiple vendor records).
It is useful to schedule an accounts payable scrubbing at least once a year, so that the vendor master file contains the most up-to-date information.