>>It sounds like using a commerical package to CAS-certify and standardize the address list would be the first step. Ask your client if they already have any CAS certification software. I'm not knowledgeable about the Canadian mail system, so "CAS" may be a U.S.-only standard, but there's likely something similar for Canada.
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>>-Bruce Allen
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>problem is .... most of their customers are not located in Canada,US, or United Kingdom. .... thus standards are non-existent.
>as an example, the guy who made a data entry program for this company simply uses Address1,Address2,Address3,Address4, Address5. He did not even attempt to figure out where the city state and 'zip code' were. Every record is a different format. The data is a mess.

Consider the expense for a brute machine first, and then try some ideas on it. One thing that crosses my mind is to chop the complete address into words, or triplets of words, sort them alphabetically (starting with whatever's supposed to be the last name) and then try to match them; the more words for two records match, the more probably the addresses are the same. In your case, you'd have the last name, street name, parts of the number and parts of the zip code matching, so it would be a good candidate. Still, I'm not quite sure you can come up with anything better than a list of good candidates. I've been matching a similar thing (school names) recently, and was lucky we got only a few dozen which needed manual matching (or simply adding into the table, once we were sure they were not there). Took just a few days to match 1500 potentially new records into a table of 6000.