The Internationaler Bootsschein is issued by the DSV, the DMYV or the ADAC and renewed every two years. YACHT calls it officially recognised across Europe as proof of ownership, though it isn't issued by an authority. YACHT's contract guide is more careful: such documents give clues but don't replace a legally binding entry in a ship register.
What a surveyor checks
The owner's name and the boat's details on the IBS against the seller and the boat. SeaHelp advises checking that the seller's name is on it. On inland waters the IBS number, with S, M or A added for the issuer, can serve as the boat's identification number.
In the report
"Internationaler Bootsschein issued by the DMYV, in the vendor's name and in date. Boat not entered in a ship register; ownership rests on the IBS and the bills of sale."