Somewhere 5 years ago the refund checks were cut. Presumably if from business checking those checks would have been entered and reconciled. If you can find those it is a matter of tying the two together.
You could create current credit memos and apply them to the ocl. The canceling of this old hanging liability will involve a credit of an asset or equity account. To keep from having to upset bank reconciliations the safest thing to do, in my opinion, is create a journal entry today, Debit Other Current Liability and Credit Owner Equity. If you have not done taxes yet you might use 12/31 as journal date.
