LACSLink®

LACS is the Postal Service™ acronym for Locatable Address Conversion System, which supports the conversion of rural-style addresses to street-style addresses. LACSLink is the Postal Service database that allows ZP4 to automatically perform conversions from one address style to another, as described below.

Most of the records in the LACSLink system are for changing rural-style box numbers to street names. For example,

RR 1 BOX 127A is converted to 17255 SCENIC RD

Some LACSLink records handle renumbered Post Office™ boxes. For example,

PO BOX 123 is converted to PO BOX 555123

Some LACSLink records handle changes when streets are renamed and the house or apartment number also changes. For example,

905 LOWER AVE is converted to 1125 FREEDOM DR

ZP4 automatically performs LACSLink conversions like those shown above. The conversion of rural box addresses to street addresses by local governments is ongoing. The LACS flag indicates if any ZIP + 4® database record includes addresses that can be converted using LACSLink.

The Postal Service prohibits using LACSLink for the manufacture of address lists. A "violation" will occur if ZP4 detects LACSLink is being used to generate address lists, and subsequent LACSLink output will be suppressed. Violation monitoring and enforcement is a requirement of the Postal Service. Semaphore Corporation is required to notify the Postal Service of your name and address upon a violation. If you repeatedly generate LACSLink violations, the Postal Service will prohibit you from continuing to use the LACSLink system.

LACSLink, SuiteLink™ and DPV® are required to determine the proper CASS™ ZIP + 4 code for an address.


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Semaphore Corporation is a non-exclusive licensee of the United States Postal Service®. The prices of Semaphore Corporation services are not established, controlled or approved by the Postal Service. The following trademarks are owned by the United States Postal Service: CASS, DPV, LACSLink, Post Office, ZIP + 4, Postal Service, SuiteLink, and United States Postal Service. [DA#4.07]