How to use Delivery point alternate logic in CODE-1 Plus  

An alternate address scheme return code of D means that CODE-1 Plus used delivery point alternate logic for an address match.  When this occurs the output matched address will be different than the input; the house number will typically be different and the input house number will be appended to the output address as potential secondary data.
      Primary Addr: 5 COND LOS FELICES UN
       City, ST: SAN JUAN, PR
       ZIP Code: 00907     Urb Name:
    USPS County: SAN JUAN
   Matched Addr: 653 CALLE UNION APT 5
 City,State ZIP: SAN JUAN PR  00907-3468
When accessing/matching using the CODE-1 Plus interactive RC (return code) screen, you will see:
Alt Addr Scheme: D
The input address matches to a ZIP+4 record on the US Postal database with a blank house range (the input house range does not exist for the street) and is flagged as an alternate record.  The ZIP+4 code for that record is then used to match to a base high rise record with the same ZIP+4 code for that ZIP Code.  That high rise record will have a specific primary number and that input house number will then be used as the secondary number.  The US Postal database carries many high rise delivery point alternate records to assist in getting mailings to their proper destination. The returned address is the address where the actual mail is delivered.
You can check the Alternate Address Scheme return code as follows:
If executing the CODE-1 Plus batch driver, use position 36-38 of the AM OUT parameter for a one-byte return code; if calling C1MATCHx, the return code will be returned in the P9OALT-ADDR field in P9OUT.
UPDATED:  April 21, 2017