Think about the CTR as a tracer document; if you want to use the CTR to find this transaction a year from now, where would you look?
The transaction is a potpurri. Check box 32, negotiable instrument cashed, and include the relevant account number on the CTR. That's the portion of the transaction that generates the CTR.
However, I would also check box 31, Negotiable instrument purchased and include the GL account number as well. Subsequent commenters may critique this part of the suggestion and you may choose to run it past FinCEN. However, the advice is in support of my stated goal of being able to use the CTR to find the transaction months later and simply describing the cash portion will not allow me to do that without additional steps..
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.