Official copy of your HAM licenses (Issued by FCC in US) should be carried with you when ever you are using your radio, as you may be asked to produce that license.
Hint: Print the wallet copy of your FCC license reduced to the size of a credit card, and take it to an office supply store to get it laminated. It generally only costs a few dollars, and keeps it in good shape.
Warning: If you are traveling out of the country, make sure you know and follow the rules for carrying or operating a radio in all countries you visit. Just because you are licensed in your home country does not grant you permission to operate in other countries.