On legal documents, you often see, "signed XYZ for and on behalf of <insert name or name of company>." This is because for and on behalf of mean different things.
'Can I sign for my friend?' = Can I sign in place of/as a substitute for my friend?
'Can I sign on behalf of my friend?' = Can I sign as the agent of my friend? (i.e., "and the implications will be as if he signed it.)
I came across THIS, which seems only to apply in AE, and not BE
Usage Note: A traditional rule holds that in behalf of and on behalf of have distinct meanings. In behalf of means "for the benefit of," as in We raised money in behalf of the earthquake victims.On behalf of means "as the agent of, on the part of," as in The guardian signed the contract on behalf of the minor child. The two meanings are quite close, however, and the phrases are often used interchangeably, even by reputable writers.