CiviCRM Duplicate Matching Threshold Configuration Tips

CiviCRM offers a function to check for duplicate contacts either manually, or on user submission.  Duplicate matching is very useful for preventing duplicate records from being created when you allow anonymous users to register for events, or make donations.  Without it, ever time an anonymous user did one of those two things, you would get a new record for them in the database. Depending on your business case, you may have a different ideas of what constitutes a duplicate contact, and therefor may have the need to set different match criteria and thresholds.  In this post I will describe a few scenarios where you may want to get really creative about your match criteria and threshold. It is worth nothing that duplicate matching works better now than a few weeks ago thanks to Jim Taylor from Rooty Hollow who squashed a long standing and undetected bug in CiviCRM’s duplicate matching that could have result in false positives, a bug we discovered through our work together for a mutual client. You can find support documentation for the Find and Merge Duplicate feature on the CiviCRM Wiki, what follows is supplemental based on my experience. Strict Matching and Individuals In CiviCRM if you go to Administer > Manage > Find And Merge Duplicates you will see a series of duplicate matching rules that are identified as either “Strict” or “Fuzzy” in the level column.  Rules that are set as strict are employed by CiviCRM when an untrusted (anonymous) user is filling out a form.  If a submission is identified as a match, information in an existing contact will be changed. It...