$100,000 Down Payment Gift vs. a GRAT on an $18M Estate: How to Calculate the Estate Tax Math in September 2026
Picture a widowed parent, call her Dana, age 68, with an $18 million estate. Her daughter just found a $500,000 house and has $25,000 saved. Dana can write a check for $100,000 tomorrow. The mortgage lender wants a gift letter, and Dana's attorney asks a question she can't answer: "Do you want to use exemption for that, or do you want to spread it out?"
That question has a real answer. It comes from a formula that fits on an index card, and most people never run it. This post walks through the formula and then tests it against two alternatives. (Dana is a made-up example, and every dollar figure below is a worked example, not a quote.)
What This Week's Data Changes (and What It Doesn't)
Three of the source articles set the backdrop:
- The Bureau of Labor Statistics' latest indicators show CPI +0.4% in August 2026, unemployment at 4.1%, and preliminary payroll growth of +162,000, with average hourly earnings up a preliminary $0.10.
- NerdWallet's Mortgage Rates Today, Friday, September 18 reports "no change" as bond markets digest the week's Fed news.
- NerdWallet's Locked Out: Should You Take 'Free Money' to Buy a Home? says homebuying assistance programs can lower upfront costs but come with trade-offs to weigh first.
Here is how that lands on Dana's decision.
Inflation and the exemption. The federal exemption is $15 million per person in 2026 and is indexed for inflation after that. One 0.4% month annualizes to about 4.9% (1.004¹² − 1). A single month is noise, not a forecast, but it shows how much the assumption matters. Indexed at 3%, Dana's exemption in 10 years is about $20.2M (15 × 1.03¹⁰). Indexed at 4.9%, it's about $24.2M. That gap of roughly $4.0M is worth about $1.6M of estate tax at 40%.
Steady mortgage rates. Both mortgage rates and the IRS 7520 rate follow Treasury yields, though the 7520 rate lags. Steady bond markets suggest the GRAT hurdle isn't lurching this week. Check the IRS's published rate for the month you'd fund, because I'm using 4.8% below as an assumption, the same one used in our break-even math at 2026's 4.8% IRS hurdle rate.
"Free money." A family gift is the other kind of free money, and its trade-off is different. Assistance programs may carry income limits or conditions, so check the terms of any program you're comparing. A parent's gift has no strings for the child, but it uses up some of your exemption, and the next section shows what that costs.
Step 1: The Formula That Makes Principal Nearly Free to Give (and Nearly Useless to Save)
Dana's estate is above her exemption, so every dollar over it is taxed at 40%. She gifts $100,000 in cash.
- $19,000 is covered by the 2026 annual exclusion. It uses no exemption.
- $81,000 is a taxable gift. No tax is due, but she files Form 709 and her remaining exemption drops by $81,000.
Estate tax saved = 0.40 × (annual-exclusion portion + growth on the whole gift)
Look at what that formula leaves out: the $81,000 principal. Giving it away removes $81,000 from her estate, but it also burns $81,000 of exemption that would have sheltered it there. The two cancel. Only the annual-exclusion slice and the growth after the gift save tax.
Here is Dana's $100,000 at 6% annual growth (an assumption), over three horizons:
| Horizon | Growth on $100K | Estate tax saved |
|---|---|---|
| 0% growth (floor) | $0 | $7,600 (0.4 × 19,000) |
| 5 years | $33,823 | $21,129 |
| 10 years | $79,085 | $39,234 |
| 20 years | $220,714 | $95,886 |
These figures assume Dana's estate stays above the exemption at death. If it doesn't, the savings are $0. The math is only "worth it" in the world where you'd otherwise owe. Your numbers will differ based on your growth rate, your exemption, and whether you're really over the line, which is why the third section of this post matters.
This is the kind of analysis Voritanel runs for you, so you don't have to build the spreadsheet yourself.
Step 2: Lump Sum vs. Five Annual-Exclusion Installments
Dana could skip the exemption entirely by giving $19,000 a year for five years and $5,000 in year six. It burns no exemption, so every dollar removed saves the full 40%.
Use the same 6% growth and a 10-year horizon:
- Gifts of $19,000 at years 0 through 4, grown to year 10, remove 19,000 × (1.06¹⁰ + 1.06⁹ + 1.06⁸ + 1.06⁷ + 1.06⁶) = $151,930 from her estate.
- The final $5,000 at year 5 removes 5,000 × 1.06⁵ = $6,691.
- Total estate reduction is $158,621, and exemption used is $0.
- Estate tax saved is 0.40 × 158,621 = $63,448.
| Approach | Exemption used | 10-yr estate tax saved | Trade-off |
|---|---|---|---|
| $100K lump gift now | $81,000 | $39,234 | Daughter buys now. Needs Form 709. |
| $19K/yr installments | $0 | $63,448 | Daughter waits about 5 years, so the house purchase doesn't happen. |
| Loan now, forgive $19K/yr | $0 | Similar to installments | Lender counts the note as her debt. The IRS can treat a prearranged forgiveness plan as a day-one gift. |
The lump sum costs Dana about $24,214 in forgone estate tax savings (63,448 − 39,234) compared with installments. That's the price of speed. Whether it's worth it depends on what the house is worth to the family, and only you can weigh that. For the annual-exclusion side of the trade-off, our breakdown of the $19,000 gift tax exclusion vs. a 4.5% CD ladder runs the same logic on a $500,000 plan.
Step 3: Does a GRAT Beat Either One?
They aren't really rivals. The gift solves a housing goal, and a GRAT solves a growth problem. But if Dana is going to think about $100,000, she should see the bigger lever too. Suppose she funds a $2 million, 2-year zeroed-out GRAT with stock, assuming the 4.8% hurdle.
Annuity payment = funding ÷ [1/(1.048) + 1/(1.048)²] = 2,000,000 ÷ 1.864691 ≈ $1,072,564 per year
At 8% growth:
- Year 1: 2,000,000 × 1.08 − 1,072,564 = $1,087,436
- Year 2: 1,087,436 × 1.08 − 1,072,564 = $101,867 left for the daughter's trust
Estate tax saved is 0.40 × 101,867 = $40,747. Because a zeroed-out GRAT uses almost no exemption, the whole remainder is tax-efficient. Now subtract costs. I'm assuming $7,500 for drafting, valuation and administration; get a real quote.
| Asset growth | Remainder to heirs | Tax saved | Net of $7,500 costs |
|---|---|---|---|
| 3% (below hurdle) | $0 | $0 | −$7,500 |
| 4.8% (at hurdle) | $0 | $0 | −$7,500 |
| 8% | $101,867 | $40,747 | $33,247 |
| 12% | $234,964 | $93,986 | $86,486 |
Notice that the 8% remainder lands at about $101,900 in two years, almost exactly the size of the down payment. Dana could gift the $100,000 now and let the GRAT remainder backfill the family's wealth transfer later. The GRAT's risks are also real:
- If growth stays below the hurdle, she loses the $7,500 and gains nothing.
- If she dies within the 2-year term, the assets are pulled back into her estate.
- If the assets are concentrated stock, a two-year swing can go either way.
For the full trade-offs, see when a GRAT beats an IDGT (and when it doesn't). To time your funding date around rate moves, see should you fund a GRAT this week.
If you want to see how your own asset, term and rate change that table, you can model this for your specific situation at Voritanel.
Step 4: The Hidden Costs Nobody Puts in the Headline
Basis. Dana should gift cash, not appreciated stock. Suppose she gifted $100,000 of stock with a $40,000 basis. The daughter inherits Dana's basis, and if she sells for the down payment she owes tax on $60,000 of gain. That is $9,000 at 15% or $14,280 at 23.8% (20% plus the 3.8% net investment income tax). If Dana held that stock until death, the step-up would erase the gain. Selling the stock herself to fund a cash gift moves the tax bill to Dana, so it doesn't disappear. The cleaner answer is to gift cash that already has full basis and keep the low-basis shares for the step-up. Our gift-now vs. die-with-zero step-up basis walkthrough covers that trade-off in detail.
Portability. Dana is widowed. If her late husband's estate never filed Form 706 to elect portability, his unused exemption may be gone, and Dana's real exemption is $15M, not more. If it was filed, she might have thousands of dollars of extra room, which could make the whole "am I over the line?" question a non-starter. This is the single biggest variable to verify first.
State tax. The federal exemption is high, but some states tax estates at much lower thresholds. Most state estate taxes don't add back lifetime gifts, though a few states add back recent ones. Check yours.
Grandchildren. If any of this money reached a grandchild instead, you'd be in generation-skipping tax territory. Annual-exclusion gifts directly to a grandchild are generally covered, and larger transfers need an allocation of GST exemption.
No exclusion for down payments. Tuition and medical bills paid directly to the provider escape gift tax. A down payment doesn't. The lender's gift letter documents that the money isn't a loan, but it doesn't change the tax treatment.
The Daughter's Side of the Math
The estate tax savings are only half the picture. Suppose the illustrative mortgage rate is 6.5%. Check NerdWallet's Sept. 18 mortgage rate page for the current one.
- Without the gift, the daughter has $25,000 down and a $475,000 loan. Payment: $3,002 a month.
- With the gift, she has $125,000 down (25%) and a $375,000 loan. Payment: $2,370 a month.
That's $632 a month, or about $75,800 over 10 years, before counting private mortgage insurance she'd avoid at 20% or more down. PMI varies by lender, but it's often quoted at roughly 0.5% to 1.5% of the loan per year. On $475,000 that's about $2,375 to $7,125 a year.
So the family-level scorecard for the lump gift is roughly:
- $39,234 in estate tax saved (10 years, 6% growth)
- about $75,800 in payments the daughter no longer makes
- $81,000 of Dana's exemption spent
Whether that beats installments, which save $24,214 more in estate tax but leave the daughter waiting, is a family decision, not a formula. NerdWallet's cruise writeup, How I Earned 1 Million Points With My Family Cruise Booking, shows how much effort people put into squeezing rewards out of a single booking. A six-figure transfer deserves at least that much modeling.
What to Plug In Before You Decide
Here are the inputs that will move your answer most, in order:
- Your true exemption, including any ported spousal amount, and whether you're over it at all.
- Your growth assumption. Try 3%, 6% and 8%. The lump gift's savings swing from $7,600 to $95,886 across just those horizons and rates.
- Your time horizon. The math above uses 5, 10 and 20 years.
- Your state's estate tax and gift add-back rules.
- The asset you'd give. Cash and appreciated stock differ by $9,000 to $14,280 in this example.
- The 7520 rate on your funding date, if a GRAT is on the table.
Change any of these and the ranking between lump gift, installments and GRAT can flip. Dana's numbers won't be yours.
If you'd like to run all six inputs side by side without a spreadsheet, you can do that at Voritanel. It models gifts, GRATs, IDGTs and portability against your own estate. Nothing here is a reason to hurry, since the math should do the persuading. But if your estate is anywhere near the line, it's worth knowing your number before the next gift letter gets signed.
Sources
- Major Economic Indicators Latest Numbers — Bureau of Labor Statistics
- How I Earned 1 Million Points With My Family Cruise Booking — NerdWallet
- Locked Out: Should You Take ‘Free Money’ to Buy a Home? — NerdWallet
- Quiz: What’s the Best Way to Make Money? — NerdWallet
- Mortgage Rates Today, Friday, September 18: No Change — NerdWallet