Ask HN: Secure use of LLMs for analyzing customer data

I would like to use ChatGPT / Claude / other "off the shelf LLMs" to analyze financial & operational data that prospects submit to my business as part of our quoting process.

We current receive data in Excel files and assign it to a team of people who take weeks to review it and prepare a proposal and estimated savings.

I believe we can do this much faster and cheaper with LLMs and that the speed trumps the accuracy (and in this case it's okay to not be 100% right)

My question: what is best practice when using ChatGPT / Claude for analyzing these files? We sign NDAs with prospects (though it doesn't specify that we would share with a 3rd party like ChatGPT). Is it enough to do a Temporary Chat?

To be clear, we have NOT done this yet - which is why I am asking. Thanks!