John Smith Revocable Living Trust account
Trustee #1
Trustee #2
Trustee #3

Trustee #1 makes reportable cash deposit into the Living Trust Account (same tax number as Trustee #1).

How to file this CTR?

Part I - Trustee #1 (box a) with Living Trust in field #8?

And additional Part I’s for Trustee #2 and Trustee #3 with box c marked?

First, unless the trust is operating a business, I would not treat this as an entity deposit.

Because it's a revocable trust, I would treat it as a simple joint account of the three trustees, but I would include the trust name in item 8 in the Part I section for Trustee #1. In all other respects, I would file the CTR as if the account is owned by the three individuals who happen to be the trustees.

Part I for trustee #1, with item 2a checked, all applicable items completed with personal info (other than #8)
Part Is for trustees #2 and #3, with item 2c checked, all applicable items completed with their personal info. No item 8 info

Our friends at FinCEN don't have any good guidance on completing CTRs for revocable trusts in any other way.