In my great state of North Carolina, we have a credit union called the "State Employees Credit Union" (SECU). This union has locations in all counties of NC. How do you map them? asked 05 Apr '16, 19:11  AmaryllisGar... |
One Answer:
It's just amenity=bank. The wiki has some suggestions for other details to add: answered 05 Apr '16, 20:50  maxerickson |
Although we certainly could do with ways to separate out different types of banks: in the UK Building Societies & former Building Societies tend to have a rather distinct offer of products & services compared with a full service 'high street' bank.
I agree, it might be worthwhile to have subtags for banks. Regarding credit unions, there's a little usage of bank=credit_union http://taginfo.openstreetmap.org/tags/bank=credit_union