Birdsong v. Commissioner: why detailed spreadsheets won

By Max Medvedev · 6 Aug 2026

Birdsong v. Commissioner, T.C. Memo 2018-148, is a taxpayer win. Detailed spreadsheets of the work performed, backed by testimony the court found credible, satisfied the regulation's "reasonable means" standard for proving participation. For an owner today it answers a narrow, practical question: the file format is free, and the resolution inside it is what decides.

What happened

Material participation was the question. The record brought to prove it was a set of detailed spreadsheets of the work performed, supported by testimony. The court found the spreadsheets detailed and the testimony credible, treated the pair as a reasonable means of establishing participation, and the taxpayer won.

That is the reported lesson, and it is worth being exact about what kind of lesson it is: a holding about the quality of a record, not a new reading of §469. Birdsong sits with the other four wins in the participation case law — Windham (T.C. Memo 2017-68), Zarrinnegar (T.C. Memo 2017-34), Leyh (T.C. Summ. Op. 2015-27) and Padda (T.C. Memo 2020-154). The losses show the failure modes. This small group shows the shape of a record that survives.

What the court held

Two things sit inside that holding, and they pull in opposite directions.

The written standard is lenient. Reg. §1.469-5T(f)(4) says participation may be established "by any reasonable means," that "contemporaneous daily time reports … are not required," and that appointment books, calendars, or narrative summaries can carry the day. Birdsong is what that sentence looks like when it works. Spreadsheets were a reasonable means. No purpose-built timesheet system was required, and none is.

The applied standard is not lenient. The same regulation governs Moss v. Commissioner, 135 T.C. 365 (2010), where the court said the regulations "do not allow a post-event ballpark guesstimate," and Sezonov, T.C. Memo 2022-40, where hours rebuilt after the fact were dismissed in the same phrase. Identical rule, opposite outcomes. The variable is never the software the record was typed into.

The tell

The tell in Birdsong is detail — specifically, detail that can be checked.

Set it against the records that lost. In Mirch, T.C. Memo 2025-128, the log claimed a flat seven hours per turnover whether the stay ran 1 day or 14, carried 744.5 of roughly 920 hours as site management and on-call time, and claimed 168 cleaning hours beside a deduction for paid cleaners. In Penley, T.C. Memo 2017-65, about 2,520 hours were claimed with no start and stop times behind them, and the court discarded the total as implausible. In Hairston, T.C. Memo 2019-104, trivial one-hour entries logged weekly rather than daily tainted the whole log.

Every one of those was a document too. What separates them from Birdsong's spreadsheets is whether a single line answers four questions: what work, on what date, for how long, and who did it. A line with that resolution invites the examiner to test it against something else — a message thread, an invoice, a calendar entry. A line reading "management, 7 hours" ends the inquiry early, and not in the owner's favor. Detail is not decoration here. It is the surface an outside record can be matched against, and credible testimony is what a court calls a person whose account keeps matching.

What this means for your records

The rule that falls out of Birdsong: the form of the record is free, its resolution is not. Four fields per entry — date, activity, duration, who did it — plus the outside records that corroborate them: booking-platform exports, guest message threads, cleaner and contractor invoices, calendar entries, supply receipts, bank records, timestamped photos.

Two structural points ride along with it. The 100-hour test in Reg. §1.469-5T(a) is a comparison — more than 100 hours and more than any other single individual — so the vendors' hours have to be documented as carefully as the owner's, which is the lesson Pohoski teaches from the other side. And a spouse's hours count as the owner's under IRC §469(h)(5), which is often the margin that clears the floor.

A log kept as the work happens produces that resolution as a byproduct. Here, entries are dated the day the work occurred, sized to the task, and treated as evidence-backed only when the entry cites an external record; a bare reminder is refused as evidence. Before anything exports, a linter reads the log the way the losing opinions read theirs — it flags a log where four in five entries are exact hour multiples, where one duration covers more than 40% of entries, and where lines went in more than 14 days after the work they describe. Those are the same tells the court named, caught while the year is still fixable.

Records worth keeping: participation logs for seven years. The ordinary statute of limitations is three years, six if income is understated by more than 25%.

Where this fits

Birdsong is the permission slip, not the method. It says a plain, detailed record is enough — which is only useful if the detail was captured while the work was happening. The rest of the mechanics live in the hub guide on how to prove short-term rental hours.

To see how a year of entries actually lands against the tests, run a reservation mix and hour split through the estimator — it evaluates all seven tests in Reg. §1.469-5T(a), shows which one carries the year, and cites the rule behind every number.