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GRAT vs. IDGT vs. Portability on an $8M Massachusetts Estate: Why No State Portability Changes the 7520 Rate Math in September 2026

Jordan and Casey are 54 and 52, live outside Boston, and have a combined net worth of $8 million — $5 million in diversified assets and a $3 million concentrated position in Jordan's old employer's stock, basis $600,000, that's been compounding at roughly 10% a year. They just got a "your estate is fine, you're way under the exemption" comment from a friend at a dinner party. They are not fine. They just don't know it yet, because the friend was only doing the federal math.

This week's economic backdrop matters more than it looks. The Bureau of Labor Statistics' August 2026 report showed CPI up 0.4%, unemployment holding at 4.1%, payrolls up 162,000, and average hourly earnings ticking up just $0.10 — a picture of an economy neither overheating nor stalling. Mortgage rates reflected that calm: NerdWallet's Friday, September 18 rate check showed no change, with bond markets still digesting the week's Fed news. When the underlying data is this stable, the IRS 7520 rate — which drives GRAT and IDGT math the same way a mortgage rate drives a home purchase — tends to hold steady too. Right now it's sitting around 4.8%. That stability is actually useful information: it means Jordan and Casey aren't racing a clock on rate movement the way estates were in April 2026's falling-rate environment or September's earlier rate jump. Their decision isn't about timing the rate. It's about a gap almost nobody tells you about: the gap between federal and state estate tax law.

The federal question is basically closed. The state one isn't.

Under the 2026 federal exemption of $15 million per person ($30 million combined for a married couple), Jordan and Casey owe zero federal estate tax today, and probably won't for a long time — even accounting for growth. That part really is fine.

Massachusetts is a different story, and it's a story other high-net-worth couples in the state have run into before. As covered in our breakdown of a $7 million Massachusetts estate still owing roughly $588,000 in state tax, Massachusetts taxes estates over $2 million at graduated rates up to 16% — and critically, Massachusetts does not offer a portability election. The federal DSUE (deceased spousal unused exclusion) that lets a surviving spouse claim their deceased spouse's unused federal exemption has no state-level equivalent in Massachusetts. At the first spouse's death, the marital deduction shelters everything. At the second death, the surviving spouse gets exactly one $2 million exemption — not two.

That means Jordan and Casey's "do nothing, rely on portability" plan works perfectly at the federal level and does almost nothing at the state level, where the actual tax bill will eventually come due.

The worked example: three paths for the $3M stock position

Assume the $3 million stock position keeps compounding at 10% a year. In 10 years, using 1.10¹⁰ ≈ 2.5937, it's worth approximately $7,781,000 — a built-in gain of $7,181,000 over its $600,000 basis.

StrategyWhat happens to the $3M positionMA estate tax impact (10-yr horizon, approx.)Capital gains tax exposure
Do nothing / rely on marital deductionStays in the estate, passes to heirs at deathFull $7.78M value taxable at second death; incremental appreciation of $4.78M taxed at an estimated ~14% marginal MA rate ≈ $669,000$0 — full step-up in basis wipes out the $7.18M gain
2-year zeroed-out GRATAnnuitized back to grantor at the 4.8% hurdle; growth above hurdle passes to remainder beneficiariesAppreciation removed from estate ≈ same $669,000 MA tax avoidedCarryover basis of $600,000 — no step-up; heirs owe tax if they ever sell
9-year IDGT installment saleSold to grantor trust for a note at ~4.8%; all growth above the note rate accrues outside the estateSame ~$669,000 MA tax avoided, plus GST exemption can be layered in for a dynasty trust (never portable, in any state)Same carryover basis issue — no step-up

This is the kind of analysis Voritanel runs for you — so you don't have to build the spreadsheet yourself, guess at Massachusetts's graduated brackets, or estimate compounding by hand.

The step-up trade-off is the actual decision

Here's what the table doesn't fully show until you run the capital gains side: if that $7.18M gain is realized by heirs after inheriting the stock with a carryover basis (GRAT/IDGT route), they'd owe roughly 23.8% federal (20% long-term capital gains + 3.8% NIIT) plus Massachusetts's 5% base rate and 4% "Fair Share" surtax on the portion of the gain over $1 million. Rough math: $1,709,000 federal + $606,000 Massachusetts ≈ $2,315,000 in capital gains tax, whenever the stock is eventually sold.

Compare that to the $669,000 in Massachusetts estate tax the GRAT or IDGT saves by moving the appreciation out of the taxable estate. If Jordan and Casey's heirs sell the stock shortly after inheriting it, doing nothing and taking the step-up wins by roughly $1.6 million — the estate tax saved is smaller than the capital gains tax created. If the heirs never sell — pass it to the next generation, hold it as a legacy position — the capital gains tax never gets triggered, and the GRAT/IDGT route wins outright.

That single variable — will your heirs hold or sell — decides which strategy is actually better for this family. It's the same logic NerdWallet describes in its piece on "free money" down payment assistance programs: the free, simple option (there, forgivable grants with deed restrictions; here, portability with no admin cost) isn't free once you read the fine print, and the more structured option (paying points, or funding a trust) only pays off if you keep the asset long enough to clear the break-even point. Neither is universally right — but your numbers will differ based on your specific situation, especially your family's actual intentions for the asset, which no generic calculator asks about. You can model this for your specific situation at Voritanel.

What this week's data actually changes (and what it doesn't)

The steady CPI, unemployment, and unchanged mortgage rates matter for one specific reason: they suggest the Fed isn't making a sudden move that would swing the 7520 rate sharply in either direction in the next month, the way it did around the mid-September FOMC meeting covered in our look at the $613K rate-jump difference between GRATs and IDGTs. For Jordan and Casey, that means there's no urgent "lock it in this week before the rate spikes" pressure. But it doesn't remove the underlying trade-off between state estate tax exposure and lost step-up basis — that math is driven by their asset's growth rate and their heirs' holding intentions, not by the Fed.

It's also worth remembering what the calm data doesn't tell you: a soft-but-stable labor market (+162,000 payrolls, 4.1% unemployment) with modest wage growth ($0.10/hour) is consistent with a Fed that could still ease later in 2026. A lower future 7520 rate would make both GRATs and IDGTs more attractive relative to today, since more of the stock's 10% growth would clear the hurdle rate. Waiting has a cost too, though — every quarter the position isn't in a trust is another quarter of appreciation staying inside the taxable estate. There's no clean answer here, only a trade-off worth quantifying for your specific growth assumptions, as we walked through in the 5-question decision framework for estates between $5M and $27M.

Don't ignore the setup and admin costs

One more line item that generic advice skips: a 2-year GRAT typically runs $8,000–$15,000 in legal setup with minimal ongoing administration once it terminates. A 9-year IDGT costs more upfront — often $15,000–$25,000 for trust drafting, valuation, and the promissory note — plus $2,000–$5,000 a year in trustee and accounting fees for the life of the trust. Against a decision worth hundreds of thousands or millions of dollars, these costs are usually rounding errors, but they should still be in the model, not discovered after the trust is signed — a lesson covered in more depth in our breakdown of what estate planning really costs beyond the sticker price.

Run your own numbers

Jordan and Casey's $8 million, their 10% growth assumption, and Massachusetts's 16% top bracket are one specific scenario. Change the state (no estate tax at all in most states), change the growth rate, change whether heirs plan to hold or sell, and the winning strategy can flip entirely. That's the whole point — there's no universal answer here, only a calculation that depends on inputs unique to your family. If you're sitting on a concentrated position, a state with its own estate tax rules, and a "we're under the federal exemption so we're fine" assumption, it's worth checking whether that's actually true. You can run the full GRAT-vs-IDGT-vs-portability comparison for your own numbers at Voritanel.

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