Sometimes an address going into the system which is entirely correct, except for the primary number, is returned with no results. How can that be, when it might just be one digit off?
That a primary (house or building) number is "incorrect" can be explained at least two different ways:
Your question probably relates to the first scenario. In that case, LiveAddress simply cannot compensate for the bad input data. Because LiveAddress must conform to rigorous CASS™ standards, it is unable to interpolate or devise, by any other means, a primary number by pure inference. Doing so would change the delivery point and render the CASS™-Certification null and void.
The second situation is common, too. In this case, the primary number the user supplied—though not the one intended—both may or may not exist. In either case, LiveAddress cannot always figure out the intent of the user from the address alone. It is unwise and volatile to assume we can figure out the user's intent.
If the primary number exists, LiveAddress will generally be able to return results. The user simply must supply a valid primary number. Other services may interpolate or assume, and may even return fake data (we've seen it—time and time again). Remember that LiveAddress will only return valid and official information.