Picture a woman at her kitchen table, sixty years after her husband bought the house for less than the price of a used car today. She loves her son. She wants to do something for him while she's alive, so she signs the house over to him. It feels generous, and it feels like the responsible thing, one fewer item for the lawyers to sort out later.

She has just handed him a tax bill she will never see. Had she done nothing and let the house pass at her death, the law would have quietly erased most of it.

The rule that makes the difference is called the step-up in basis. It is one of the largest tax breaks in the American system, and most families have never heard of it. They only find out about it afterward, usually when it's too late to use.

What "basis" actually means

Basis is the number the IRS subtracts from your sale price to decide how much profit you owe tax on. Usually, it's what you paid, plus certain improvements.

Say your parents bought a house for $60,000 decades ago. It's now worth $400,000. If they sold it, they would owe capital gains tax on a $340,000 gain, less whatever exclusions they qualify for. (These figures are illustrative, not from any real case.)

That gap between what something cost and what it's worth is called unrealized gain. It's invisible while you hold the asset. It becomes real the moment you sell.

What happens at death

Under Section 1014 of the Internal Revenue Code, property that passes because someone died generally takes on a new basis equal to its fair market value on the date of death.

The house is worth $400,000 on the day your parent dies. Your basis is now $400,000. If you sell it for $405,000 next spring, you're taxed on $5,000 of gain, not $345,000.

The decades of appreciation aren't taxed to anyone. The IRS doesn't collect it from your parent's estate (unless the estate is large enough to owe estate tax, which most aren't, as we covered in our piece on the 2026 exemption). It doesn't collect it from you either. It simply disappears.

Inherited property also gets long-term holding-period treatment automatically, even if you sell it a month after inheriting. That's a smaller detail, but it matters.

The gift trap

Now compare what happens when your parent gives you the house while alive.

Gifted property generally keeps the giver's original basis. This is called carryover basis, under Section 1015. You receive the house, and you also receive your parent's $60,000 basis, along with the $340,000 of embedded gain. When you eventually sell, the tax comes due, and it comes due on you.

The gift looked like generosity. In tax terms, it moved a liability from a parent who would have taken it to the grave to a child who has to pay it.

This is the quiet logic behind a lot of well-meaning estate advice going wrong. Our article on adding a child to a house deed covers the legal risks of that move. The tax side is the one people discover last.

There are real reasons to give assets during life. Medicaid planning, controlling who manages what, or simply wanting to see your children benefit. But for highly appreciated assets, such as the family home, a long-held stock position, or a small business, the tax cost of giving early can be enormous. It should be a deliberate choice, made with the numbers in front of you, not a default.

Where the step-up applies, and where it doesn't

The rule isn't universal, and the exceptions are where families get hurt.

It generally applies to: real estate, stocks, mutual funds, and other capital assets held in your own name or in a revocable living trust. A revocable trust doesn't change the tax result, because the assets are still treated as yours until death.

It generally does not apply to: traditional IRAs, 401(k)s, and similar tax-deferred retirement accounts. Those hold untaxed income, not appreciation, so there is nothing to step up. Heirs owe ordinary income tax on withdrawals. (We unpack that in our article on the inherited IRA 10-year rule.) It also generally doesn't apply to assets you've already given away through a completed gift, and many irrevocable trusts fall in the same category unless the assets are included in your taxable estate.

A special case in community property states: when one spouse dies, both halves of community property can receive a new basis, not just the decedent's half. The surviving spouse gets a full step-up on property they co-owned. In most other states, only the deceased spouse's share steps up. If you live in one of the community property states, or have moved between them, this can be worth real money and is worth confirming with a professional.

Alternate valuation: an executor can sometimes elect to value the estate six months after death instead, but only when that lowers both the total value and the estate tax owed. For most families this never comes up.

The part everyone skips: proving the number

The step-up is automatic in law. In practice, it is only as good as your ability to prove the date-of-death value.

Imagine selling an inherited house six years later, and the buyer's closing statement shows $410,000. You tell your tax preparer the basis is the value when your mother died. Your preparer asks, reasonably: what was that? If nobody wrote it down, you're reconstructing it from old listings and memory, and the IRS is under no obligation to accept your guess.

A qualified appraisal, dated as of the death, turns an argument into a document. The cost is typically small compared with the tax at stake. The same goes for brokerage accounts: the statement showing values on the date of death is the evidence.

This is also why the work of settling an estate rewards good records, a theme that runs through our piece on why the paperwork takes a year.

Your next moves

  • List the appreciated assets. Write down every asset your family holds that is worth far more than it cost: the house, a vacation property, long-held stock, a business interest. Next to each, note your best estimate of the original purchase price. This is your "embedded gain" list.
  • Before any gift of an appreciated asset, ask for the comparison. Have your accountant or estate attorney run two scenarios: giving it now versus leaving it at death. Ask specifically for the heir's tax bill under each. Don't sign a deed or transfer until you've seen both numbers.
  • Check how each asset is titled. Confirm whether it's in your name alone, jointly, in a revocable trust, or already in an irrevocable one. The title decides whether the step-up is available. Note which state you live in and whether it's a community property state.
  • Keep purchase and improvement records in one folder. Closing statements, receipts for major renovations, and old brokerage confirmations. Even with a step-up, these matter for assets you're not sure will qualify, and for any property that was gifted to you earlier.
  • After a death, order the appraisal fast. If you're an heir or executor, hire a qualified appraiser for real estate and business interests, with the valuation date set to the date of death. Save the report and the date-of-death account statements alongside the estate file.

Why we built Heirloom around this kind of question

The step-up in basis is a perfect example of how estate planning rewards people who see the whole picture instead of one decision at a time. The gift, the title, the account type, and the records all interact, and the right answer is rarely the one that feels most generous in the moment. Heirloom exists to lay your assets, how they're titled, and who gets what onto a single map, so a choice like "should I deed the house to my son?" gets weighed against everything else it touches. If you'd like to see your own estate that way, you can start at heirloom.lumenlabs.works. This article is general information, not tax or legal advice, so confirm the details for your state and situation with a professional.