What is a DLN?
A DLN is a Document Letter Number — a unique number which is printed on every piece of correspondence relating to CAPP-enabled taxes since November 2008. The DLN can be found in the lower left of any bill, letter, or return sent relating to a CAPP-enabled account, including the CAPP welcome letter. If the correspondence includes a payment voucher, the DLN will be located above the voucher perforation.