Nope. But then, I only makes cakes for family and friends now. I hope I don't need a contract with them! I think they'd know their inexpensive (not cheap!) cake supply would become nonexistent if they ever complain...... ;-)
I am actually starting to write out receipts. My opinion is that you should always put it in writing. Nothing necesarily fancy but something that briefly explains things like nonrefundable deposits etc.
I have one I use for weddings, and big orders and such so I just use it all the time now to keep myself used to doing it and I wouldn't want one customer to tell another I had HER sign a contract so why didn't everyone need one too! Ya know how that stuff goes!
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make, bake, decorate......what else do you need?