W4 Denial Code (Deactivated) – Use P15

W4 is a retired claim adjustment reason code. Payers stopped using it on 07/01/2014. Current remittances use P15 instead.

Seeing W4 on a Remittance?

W4 was retired effective 07/01/2014 and should not appear on new remittances.
Payers now report this situation with P15 — check that page for current guidance.
Official retirement note: Use code P15
If W4 appears on an old ERA you are reworking, interpret it per the remittance date, then follow the current code's guidance for any corrected claim.