We have to keep copies of the rabies certif for appropriate govt entity - be it city, county or state. Never in 37 years has the govt asked for their copy. With computers, it's a very simple report to print out.
Our main problem is that licensing is a city thing. We have clients from at least 20 different cities, each with their own licensing. Having to purchase tags and licenses from every city would be a major pain.
Being on the state line between IL and IN, we have a number of clients who live in Cook county, IL and they have a county wide system. We buy special Illinois tags (includes the licensing for either 1 or 3 years depending on vaccine used) and the copy is sent to the Dept of Animal Control and they do keep track. We do a tack on fee in addition to the rabies vaccination cost and that covers the cost of the license.