"Acceptable forms" refers to the different types or formats that are considered reasonable or appropriate in a particular situation or context. Full definition
For more information on identification to use when you vote for the first time, check the complete list of acceptable forms of identification. (politics.stackexchange.com)
If your pet has a current rabies vaccination, please bring proof in the form of a certificate (tags are not acceptable forms of proof). (poaspay.org)
Mad at what some people see as acceptable forms of entertainment. (relevantmagazine.com)