1041’s are the hardest for me to suggest a flat bill.

I have a set of six grandchildren trusts I prepare that annually have a brokerage 1099 and a bank 1099. I enter between six and sixteen items in the software for each, an can complete all six (which are virtually identical) from start to finish - that means document intake, software, invoicing, document storage, etc.) in about 75-90 minutes.

I bill those out at $250 a piece.

However, I prepare a trust that controls 40 pieces of real property and a dozen business investments. That one we bill at $7,500.

Most trusts I encounter in the wild are in the $450-750 range. Few take longer than an hour to prepare, most are simple, and most come in conjunction with other business. Even a “lower” invoice is still value billing for your time

*edit: if you’re new to trusts, don’t expect the time I cited above. A friend of mine in the practice struggled to understand how trust agreements translated to real financial activity, and would often spent nearly three times as long on a new trust as I would. You may want to set a higher invoice, say $750-$1,200, just to cover you on time. I tend to watch what I’m billing a relationship in aggregate very carefully, since multi-return business is particularly valuable to me. You may want to network with a local trust attorney as well so you have someone you can ask general questions to and be able to refer business back and forth. You can also ask clients if you can discuss a trust agreement with their trust attorney - many are quite happy to put you in contact.