I'd looked at Claude recently, but didn't see a custom GPT capability. Granted, I may have not looked hard enough. I've fiddled a bit with Gemini and Copilot, but didn't look into their business / custom GPT capabilities.

I'm looking for a custom GPT capability that would allow me to "teach" the system some tax rules and application of the rules against a number of variables in raw data. We'd be uploading spreadsheets of raw data into the GPT and then asking it to analyze the data and export a csv file with tax coding. It'd also be nice if it could summarize it's output. Basically, trying to see if it could replace some tax form prep steps we manually do in Excel. I'd need a GPT to do it so that we could tweak it's capabilities over time and repeat the same process over and over. In theory, at least.