Once files have been turned over to the collection agencies, there are no local clothing stores holding clothing documents to accept returns against. When units are processing Reserve releases, particularly those who have been identified as Non Effective Strength (NES), i.e., having failed to parade for a certain number of training dates, registered letters will be sent to the last known address declaring the intent to release. Immediate response to these letters is pretty much the last chance the member has to return kit before clothing documents are removed from the local issuing store and forwarded to higher headquarters. At that point the local unit has closed the file and the only remaining transaction to be settled is the member's monetary debt in th hands of the collection agency.
Unless something has changed in the past few years, I know of no way the file can be "reopened" to accept kit in lieu of the cash.
Someone currently working with NES files in a reserve unit may have more up to date information.