Personal Use Days on a Rental Property: The 14-Day Test.

A couple rents their beach house 200 days in 2026 and spends 25 nights there themselves: two weeks in July, a long weekend in October, a few nights in March opening the house. The house ran a real loss, and they expect to deduct it. They can't. Personal use days on a rental property are measured against a threshold that 20 nights clears and 25 does not, and crossing it makes the house a residence for the whole year.

The rule is one sentence. §280A(d)(1) treats you as using a dwelling unit as a residence if personal use exceeds the greater of 14 days or 10% of the days it is rented at a fair rental. The denominator is days actually rented, not days listed. A cabin that sits on a booking site all year and rents 40 days has a 14-day ceiling, not a 36-day one, and that catches more owners than the busy beach house does.

The word is exceeds: 20 personal nights against 200 rented nights keeps you out, 21 puts you in. There is no proration and no reasonable-cause relief on the count, which is the part owners find hardest to believe.

Nights rented below market count against you. Under §280A(d)(2)(C), a day someone occupies the unit at less than a fair rental is a personal use day, so the discounted week you gave a friend at $60 a night leaves the rental column and joins the personal one. One week moves the ratio twice.

§280A(d)(2)(A) counts use by you or by a family member as defined in §267(c)(4): brothers and sisters (whole or half blood), spouse, ancestors, and lineal descendants. Your brother's week is your personal use even if he paid full market rent. Cousins, nieces, and in-laws are not on that list, so their fair-rental stays are rental days. §280A(d)(3)(A) carves out a fair rental to anyone, family included, who uses the unit as a principal residence: a house rented year-round to a parent is a rental, a house lent to a parent for August is not. Swapping weeks with another owner counts under §280A(d)(2)(B), and so does a week donated to a charity auction, since the winning bidder paid the charity rather than you.

Repair days are the one real escape hatch. The flush language of §280A(d)(2) says a day spent on repairs and annual maintenance on a substantially full-time basis is not personal use, and that it stays that way even if the other people on the premises are not working, so the family can be at the beach while you replace the deck boards. What it will not survive is a thin record: any part of a day counts as a whole day, and the burden of proof is yours. Photos, receipts, and a dated log take ten minutes a trip.

§280A(c)(5) limits deductions allocable to rental use to gross rental income, in a fixed order: mortgage interest and property taxes first, then operating expenses, then depreciation. Rental use can never produce a loss. What the ceiling squeezes out carries forward subject to that same limitation, whether or not the unit is a residence in the later year, so it only ever comes back against future rental income from that house.

Then §469(j)(10) closes the other door: if a dwelling unit is subject to §280A(c)(5) for the year, income, deductions, gain, and loss allocable to that use are not taken into account under §469 at all. No $25,000 active participation allowance, and the short-term rental loophole, which turns losses non-passive when average stays run seven days or less, does nothing here. A house that is a residence for the year has no loss left for §469 to characterize.

§280A(e)(1) allocates rental expenses by days rented at a fair rental over total days used. Days the house sat empty count in neither half of that fraction, which is why 200 rented and 25 personal gives 88.9% rather than 200 of 365. Publication 527 applies that ratio to every expense, mortgage interest and property taxes included.

The courts do not. §280A(e)(2) says the subsection does not apply to deductions allowable whether or not the unit was rented, and interest and taxes are exactly that: they accrue across the year regardless of use. In Bolton v. Commissioner, 694 F.2d 556, the Ninth Circuit allocated them by rental days over 365, and the Tenth Circuit agreed in McKinney v. Commissioner, 732 F.2d 414. The IRS has never acquiesced, and the Tax Court has kept ruling for taxpayers.

In Case B that method puts $16,438 of interest and taxes in the first tier instead of $26,667, leaving $21,562 of rental income for the tiers below. Operating expenses clear in full, depreciation gets $9,118 of its $10,667, and the carryforward drops from $11,778 to $1,549. The $13,562 pushed off Schedule E lands on Schedule A, where the interest is second-home interest and the tax counts against the $40,400 SALT cap for 2026.

Use it when the ceiling binds and not otherwise: in a year with no cap the Publication 527 ratio puts more interest on Schedule E anyway. Outside the Ninth and Tenth Circuits you are relying on Tax Court precedent against a position the Service still asserts, so work the numbers both ways and keep them in the file.

First, §280A(g) is a different rule that shares a number: rent a home 14 days or fewer during the year and the income is excluded entirely, with no deductions against it. That is the Augusta rule, and it points the opposite way from the personal-use test in §280A(d).

Second, staying under the line costs something too. §163(h)(4)(A) makes a second home a qualified residence only if you use it as a residence within the meaning of §280A(d), so the personal use that costs you the Schedule E loss is what keeps the mortgage interest deductible on Schedule A. Fall to 20 nights and the personal share of that interest is nondeductible personal interest. Above, that is $2,444 traded for a $12,909 loss, an easy call. On a big mortgage and a thin loss it is not.

If you are near the line, every lever is in the count: repair trips documented well enough to survive a question, a below-market week repriced to market, a family stay that does not land on the §267(c)(4) list. Days are worth the whole deduction here, so decide it in June, not the following April.