Keeping the reciept for your boat batteries...

[bassadict69]

A handy place I have seen to keep your reciept for your batteries is right on your battery. Get either a plastic paking list enclosure (like you stick on packages) or simply stick in a zip lock bag & tape to the side of one of your batteries using duct tape.

This way, should your batteries bite the dust in 11 months, you don't have to  hurt yourself trying to remember where you stashed the reciept.