Is there a standard check format in the USA?
Nope, anything is that has the required information is fine.  At a minimum you need to have the routing number, account number, amount, "pay to" line and a signature. The only laws are that it can't be written on anything illegal, like human skin, and it has to be portable, not carved on the side of a building ( for example) https://www.theguardian.com/notesandqueries/query/0,5753,-20434,00.html http://www.todayifoundout.com/index.php/2013/12/people-actually-cash-big-novelty-checks-even-possible/ That said, the MICR line and standard sizes will make things eaiser for they bank, but are hardly required.  You could write your check on notebook paper so long as it had the right information, and the bank would have to "cash it". Keep in mind that a check is an order to the bank to give your money to a person and nothing more. You could  write it out in sentence form. "Give Bill $2 from account 12344221 routing number 123121133111 signed _________" and it would be valid. In practice though, it would be a fight. Mostly the bank would try to urge you to use a standard check, or could hold the funds because it looks odd, till they received the ok from "the other bank". But.... If you rant to fight that fight....