AKC tracks them for you. However, it's a good idea to keep track of your passes. A Blackhawk Club member did not receive her MH Certificate and found out that the AKC failed to record one of her passes at an event. The AKC gets the pass results from the Hunting Test Secretary, and the AKC was able to look up the passes for the test that this person passed, and ultimately issued her MH certificate.
As the Hunting Test Secretary, I keep a results for events and have them back to 1997 when I started doing the job. I suppose I could throw them, since most of the dogs that passed a test in 1997 are probably no longer with us
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