Locatable Address Conversion System
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Locatable Address Conversion System (LACS) is a service offered by the United States Postal Service to update mailing addresses when a street is renamed or the address is updated for 911. In the case of 911, the address is changed from a rural route format to a urban/city route format. E.G. RR 2 BOX 8, SOME CITY, TX would become 2601 BELMONT DR, SOME CITY, TX.
A check of address using LACS is typically not performed by the USPS, but by 3rd parties who license the LACS data from the USPS. A license will create or purchase software to perform the LACS check, receive periodic updates of LACS data from the USPS, and submit reports to the USPS about how the LACS data was used.