Codex · OpenAI
Prepare a complex owner tax return and check it against your CPA
A startup founder whose year included a company sale and four partnership K-1s had Codex gather documents, interview him and compute the return, while an accountant prepared it in parallel. Codex's numbers exposed an item the accountant had missed.
What they did
He worked in a local folder with his prior-year return, then dictated a long brain dump of the year's tax facts. Codex asked follow-up questions and recorded every fact and decision in a README. It pulled tax forms from his email and financial sites through a browser tool while he did each sign-in himself, then wrote a Python tax engine that filled the forms.
How it went
The poster says the accountant's first estimate came in noticeably lower than Codex's. Codex traced the gap to a post-closing escrow payment from the sale that the accountant had not tracked, and the accountant then revised to nearly match.
Worth knowing
He says he never reviewed the generated code and does not recommend most people rely on a homemade tax engine. Two K-1s were still outstanding, so the return was not final.
Try it with Codex
Read my prior-year return in <your tax folder> and then interview me about this year's income, sales of assets and deductions, saving every answer to a notes file. List the forms you need and wait while I download them into <your documents subfolder>. Compute the return, show each figure with its source document, and give me a list of open questions to take to <your accountant>.
We wrote this prompt from the case. Replace the parts in angle brackets with your own details.
What this label means: User reports
Someone using it at work posted about it. Any numbers are theirs, so we write "the poster says".
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