Lorimer (LP10) letter

[theboyfold]

I've been told that I have to supply a letter to a company that I'm doing some freelance work with that I'm happy to arrange my own taxes so they can pay me my gross earnings and I will take care of my taxes.

Is there anything that I need to specify within my letter, or can I just say that I'm happy to take care of my own tax and you can pay me my gross earnings?