At 70 He’ll Move Into His Daughter’s In-Law Suite and Pay Her $1,500 a Month. She May Owe Tax on It, Unless It’s Really Just Sharing Costs

They agreed on the number at the kitchen table. The result is that when Dad turns 70, he moves into the in-law suite off the garage and pays his daughter $1,500 a month. It felt fair to everyone, and nobody brought up taxes.

Lots of families are making this same deal as parents age. It works out to $18,000 a year going into the daughter’s account. Whether she owes tax on that money depends on what the money actually pays for.

Why $18,000 a Year Matters to Both Sides

For him, it’s a big share of retirement income. The average retired worker’s Social Security check is about $2,071 a month in 2026, and his Medicare Part B premium alone is $202.90. For her, federal law lists rents as gross income under 26 U.S.C. § 61(a)(5). If the payment counts as rent, it goes on her return.

Rent or Reimbursement Decides Everything

Rent is money paid for the right to live in a space. Cost sharing is different. That’s Dad covering his own groceries, his slice of the electric bill, and the extra water he uses. When money just passes through to pay for what he buys, she isn’t really making anything from it.

IRS publications don’t draw a bright line between the two for families. That gray zone is exactly why a tax pro is worth paying here, and it’s one of a handful of quiet rules that can cost retired people real money (we covered nine of them in a free guide to the retiree tax traps worth a look before Dad moves in). A one-hour review of the paperwork can help you agree on which side of the line the arrangement sits on.

If it’s rent, the family rules kick in. The tax code handles a family member’s use of a home as personal use unless the unit is rented at a fair rental rate as that person’s principal residence. Charge Dad below market, and the IRS generally treats the suite as personal space. She still has to report payments that count as rent, but she generally can’t deduct the suite’s expenses as rental expenses. Certain personal deductions, such as mortgage interest and property taxes, may still apply.

Running the Numbers Both Ways

Say the suite’s share of property tax, insurance, utilities, and repairs runs $7,000 a year.

So the rent version adds about $11,000 to her taxable income every year he lives there. Cost sharing only works if the dollars actually match his real costs. A flat $1,500 that has nothing to do with the bills looks a lot more like rent.

What Dad Gets, and What He Doesn’t

Paying rent on the home he lives in doesn’t give him any deduction. It’s a personal living expense.

Could she claim him as a dependent instead? A parent can be a qualifying relative if his gross income is less than $5,300 (the 2026 figure) and she provides more than half of his total support. Social Security generally doesn’t count toward

But his own $18,000 a year goes toward his own support, which makes the over-half test hard to pass. If it does pass, it’s worth up to $500 through the credit for other dependents.

Medical home changes like grab bars can count as medical expenses if their main purpose is care for a dependent who lives with you. They only help once total medical costs pass 7.5% of AGI.

A Surprise Waiting When She Sells

She can exclude gain on her home if she owned and lived in it for 2 years or more during the 5 years before the sale. If the rented space is inside her living area, like a spare bedroom, she doesn’t need to split the gain. Even so, any depreciation allowed or allowable after May 6, 1997 gets taxed back. That means depreciation she was entitled to take counts even if she never claimed it.

A suite that works as its own separate unit can be handled like the rented half of a duplex. Gain on that part isn’t excluded unless she lived in it herself. Before he moves in, she should also check that her homeowner’s policy covers a paying resident and that local zoning allows the unit.

Put the $1,500 in Writing Before He Moves In

The one thing to write down is what the monthly payment covers. Choose one setup and stick with it:

• Cost sharing: List his groceries, utilities, and household costs, and tie the payment to those bills. If costs go up or down, adjust the number.
• Rent: Set it at fair market rent, report it, and deduct the suite’s expenses. Keep in mind that depreciation recapture shows up later when she sells.

The mistake to avoid is a vague, below-market “rent.” It brings the worst of both: income she has to report, limited deductions, and recapture down the road.

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