How to use Codex to collect card statements for tax
Codex collected 33 card-statement CSVs and prepared an accountant email; the owner handled login, corrected a false reason and approved the ZIP before sending.
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Original prompt
Shared by the source author. See source notes for context.
半年分の明細を集めて
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See placements →What happened
The account reports 33 organized CSVs in an approved ZIP sent to the accountant, with a visible sent confirmation; no tax calculation is claimed.
Reported by 本郷喜千 (@yoshiyuki_hongoh) — noteHow the agent did it
- Codex collected card CSVs while the owner authenticated and corrected portal and month interpretation errors.
- The agent separated holders and sources, deduplicated files and prepared the ZIP and Gmail draft.
- The owner corrected an unsupported rationale, reviewed the complete message and authorized sending.
Where a person stepped in
The owner controlled login, two-factor steps, portal corrections, record exclusions and final email approval, including correcting an invented explanation.
本郷喜千 used Codex to collect six months of card statements and send the approved packet to an accountant. The records included personal, corporate and sole-proprietor contexts, so keeping ownership and mailing scope straight was part of the task.
Codex navigated statement portals, downloaded CSVs and organized them with holder, source and month in the filenames. The owner handled login and two-factor authentication, corrected a railway-portal route and clarified the difference between billing month and usage month. Months without charges were checked on screen rather than treated as missing downloads.
The resulting packet contained 33 CSV files in a 29 KB ZIP. Codex prepared a Gmail message, but introduced an unsupported explanation for excluding bank data. The owner stopped that change, required a check against recent Gmail evidence and restored the approved rationale.
Only after recipient, subject, body and attachment review did the human authorize sending; the account records the sent confirmation. This is a concrete financial-paperwork workflow, not a claim that Codex calculated tax. Some bank records were deliberately outside this mailing, and the agent’s incorrect rewrite made the final human review consequential.
Prompt
Original prompt
Source: note · 本郷喜千 (@yoshiyuki_hongoh)
Frequently asked questions
Did Codex prepare a tax return?
No. The documented task was collecting, organizing and emailing approved statement files.
How were no-charge months handled?
The workflow checked the portal screen instead of assuming the absence of a CSV meant a failed download.
What error required human correction?
Codex rewrote the reason for excluding bank data without support; the owner restored the approved explanation before sending.
More details
About this account
Codex collected card CSVs while the owner authenticated and corrected portal and month interpretation errors. The agent separated holders and sources, deduplicated files and prepared the ZIP and Gmail draft.
Full Japanese primary article opened. Original prompt excerpt. Mixed personal and business records are explicitly disclosed; excluded bank material and the corrected email rationale are preserved. Sent confirmation is reported in the source. Original prompt excerpt.
Credit: 本郷喜千 (@yoshiyuki_hongoh) — note
Source published 17 Jul 2026
Source checked 14 Oct 2026
Tools and topics
Codex · Card portals · CSV · ZIP · Gmail
statement collection · account separation · email approval
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.