Grouping is the set of rules in Treas. Reg. §1.469-4 that decide what counts as a single "activity" for purposes of IRC §469. If two or more of your short-term rentals form what the regulation calls an appropriate economic unit, they can be treated as one activity, and participation is then measured across the group rather than property by property. Grouping does not create hours, and it does not reach every test in the strategy. It changes the unit the hours are measured against.
What follows is the shape of the rules. Whether a grouping is available on your facts, and whether it is wise, are questions for the person who signs the return. Our interest is narrower: what the log must contain so the question can be answered at all.
Why grouping comes up in the first place
Section 469 operates on activities, and the material participation tests in Treas. Reg. §1.469-5T are applied to an activity for a taxable year. Absent a grouping, each property is generally its own activity, so each one has to clear a test on its own hours. Owners who think in portfolio terms tend to discover this late. The arithmetic of that default — and why three properties at 70, 50 and 40 hours is three failures rather than one success — is worked through in the post on per-property versus combined hours.
Grouping is the mechanism that changes the unit being tested. It is not a year-end calculation and not something a tracking app performs. It is a position taken on a return.
What the regulation actually asks
Treas. Reg. §1.469-4(c) sets a facts-and-circumstances standard: activities may be treated as a single activity if they constitute an appropriate economic unit for measuring gain or loss. The regulation gives five factors the greatest weight, and says plainly that not all of them are necessary:
- similarities and differences in the types of trades or businesses
- the extent of common control
- the extent of common ownership
- geographical location
- interdependencies among the activities — whether they share books and records, employees, customers, or buy and sell between each other
The regulation also allows a taxpayer to use any reasonable method of applying those facts and circumstances. That latitude is real, and it is why practitioners differ about identical-looking portfolios. Two cabins on one lake with one cleaner and one calendar read differently from a Florida condo and a Utah ski unit in separate LLCs with different co-owners — but the regulation does not reduce to a mileage rule, and the second grouping is not automatically wrong.
Whether a short-term rental is a "rental activity" here
This wrinkle is specific to our readers and worth stating precisely. Treas. Reg. §1.469-4(b)(2) defines rental activities for grouping purposes by cross-reference to Treas. Reg. §1.469-1T(e)(3) — the same provision whose exceptions take property with an average period of customer use of seven days or less outside the rental definition. Paragraph (b)(1) defines trade or business activities so as to exclude rental activities.
The consequence many practitioners draw is that a qualifying short-term rental is not a "rental activity" for §1.469-4 purposes at all, which means the extra limitation in §1.469-4(d)(1) — the one that lets a rental be grouped with a trade or business only where the rental is insubstantial, or the business is insubstantial, or ownership is proportionate — is addressed to something else. A portfolio that mixes short-term and long-term rentals is where this gets genuinely difficult, because the two sides of it may sit in different categories under the same regulation.
We are describing a reading, not endorsing one. Raise it with your preparer as the question about categories that it is.
What grouping changes, and what it does not
Grouping changes the activity. Everything downstream of that definition moves with it:
| What is measured | Separate activities | Grouped as one activity |
|---|---|---|
| Hours tested against 100 or 500 | Per property | Across the group |
| "More than anyone else" comparison | Per property | Against all other participants in the group |
| Suspended losses tracked | Per property | For the group |
| Average period of customer use | Per property | Still per property |
Two cautions follow. First, the comparison prong of the 100-hour test moves both ways: a group's hours are compared against the combined hours of everyone else who participated in the group, so adding a property adds its cleaner's hours too. Grouping can take a portfolio further from passing, not closer.
Second, grouping says nothing about the 750-hour real estate professional route, which has its own aggregation election under §469(c)(7)(A) and its own requirements. The 750-hour test guide covers that path. The two elections are often confused in the same conversation.
The seven-day test does not merge
The average-period-of-customer-use computation in Treas. Reg. §1.469-1T(e)(3)(ii)(A) is derived from the actual stays at a property. It is not a participation test, and grouping for participation purposes does not blend it. A cabin averaging four nights and a condo averaging nineteen do not produce an eleven-night portfolio figure.
So a grouped portfolio can still hold properties on both sides of the rental definition. Keep the stay-and-night counts per property, whatever you do with hours. No log computes that figure; it comes from the stays shown on the booking platform, and it belongs in your records property by property.
Consistency, regrouping and the disclosure statement
Three features of the rules make grouping a decision rather than a preference.
It binds you. Under Treas. Reg. §1.469-4(e), a grouping once made generally must be used consistently in later years. Under (e)(2), regrouping is permitted only where the original grouping was clearly inappropriate or a material change in the facts makes it so. A grouping that helps in a loss year can be awkward in a year when one property has income or is sold.
It is disclosed. Rev. Proc. 2010-13 requires written statements reporting groupings, additions of a new activity to an existing grouping, and regroupings, filed with the return. There is relief in the procedure for a year's missed disclosure on stated conditions, but the baseline is that the position is affirmatively reported rather than inferred from Form 8582.
The Commissioner can regroup. Treas. Reg. §1.469-4(f) allows the Commissioner to regroup activities where a taxpayer's grouping fails to reflect an appropriate economic unit and a principal purpose is circumventing §469. IRS Publication 925 describes the grouping rules in plain terms.
Log so that either grouping works
None of the above is a reason to log differently. It is a reason to log one way and keep the option open.
Tag the property on every entry, without exception. An entry that says only "rentals" cannot be assigned to a property later, and it cannot be assigned to a group either, because a group is a named set of properties. Where an hour genuinely covered two properties — a shared supply run, a portfolio call with the insurance broker — split it by a reasonable method and record that method in the entry.
With property tags in place, both arithmetics come out of one file. STR Tracker's Hours by Property report shows each property's running total alongside the combined figure, so the per-property and grouped views are the same record read two ways. A spreadsheet does this too, as long as the property column is never empty.
Record every other participant's hours by property for the same reason. The comparison prong cannot be evaluated for a group without them.
Questions worth putting to your preparer
- Are these properties an appropriate economic unit under Treas. Reg. §1.469-4 on these facts, and which factors carry the weight?
- Does a grouping already exist from a prior year that I am bound by?
- Which category does each property fall into under Treas. Reg. §1.469-1T(e)(3), and does mixing short-term and long-term rentals change the analysis?
- Given my hours and the other participants' hours, does grouping change the outcome, or am I short either way?
- What does the Rev. Proc. 2010-13 statement need to say, and who prepares it?
Question four is the one you can prepare for without help. If your log cannot answer it in five minutes, the log is what to fix first — the election is a conversation about numbers you have to be able to produce. Start a log with the property on every entry and the question stays open all year.