Draft S-corp tax calculations from bookkeeping records
A developer had Claude Code build tax-calculation scripts from bookkeeping files, then used Codex to audit the logic and catch an incorrect Schedule L mapping.
- What they did
- They stored bookkeeping exports from QuickBooks along with bank records in a private Git repository. Claude Code, running on Opus 4.6, then wrote Python that reads those files and computes the numbers needed for the S-Corp forms. Codex, using a high-reasoning model, checked the scripts; the developer steered the process and compared the outputs with the underlying data.
- How it went
- Codex reported three problems in the 1120S code. The most serious was that Schedule L Line 18 used total liabilities when it should have been based on other current liabilities. The developer also uncovered some 2025 bookkeeping errors on their own.
- Tips
- Treat the agent’s output as draft work, not a filing-ready return. Ask for a trace from each calculated line back to the source rows, and review the final numbers yourself before anything is submitted.
Try it yourself with Claude Code
In [folder], use my [year] QuickBooks export and bank records to build Python scripts that calculate the amounts needed for my S-Corp return, including the income statement, Schedule L, and shareholder items. Then inspect your own code and outputs against the source files, point out any mismatched totals or uncertain mappings, and stop before any submission step so I can confirm the final version. Give me a concise handoff file with each figure tied to the source data for my accountant.
Fill in the [brackets]. Agents can make mistakes, so review anything before it is sent, paid or deleted.
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