I once knew a founder of a pre-GPT-3 AI product that analyzed certain cost-adjacent documents to find "hidden" optimizations. The "AI" was the founder, an expert in that industry, churning through the uploaded documents himself and writing reports by hand detailing potential cost savings. How far we've come!
Some people suspect that is still how many of the AI startups operate
Create a known good OCR to calculation mechanism, then generate reports based off it. If it is inaccurate, its probably a small amount of logic to fix it.
With GPT you could even get it to write the parsing logic for you perhaps, and maybe process bill data when a bill doesn't exactly match existing parser data.