In the US. they are very strict about displaying your registration number.(Issued by the Dept of Motor Vehicles)
The first 2 letters are the state followed by ID numbers.
They have to be set out on the bow in block letters at least 3" high in a contrasting colour. The state decal is then placed 3" aft of the numbers.
As well as this you must carry your actual registration whenever on the water. If you dont have a current decal or "tag " you will get pulled over and ticketed very quickly
The State decal (blue sticker ) was obtained annually;(but now Bi-annually I think) and costs about $10.00
Because over here inflatables are not as common as the UK ;many SIB/RIB owners go for the cheaper method of just sticking numbers to a plate and hanging it on the bow.
In fact as its so expensive to get suitable cut lettering over here,it was cheaper for me to send to the UK for mine and got them done in flexi-vinyl, which seems to work great so far