What is settled
The estate tax itself is an excise on the transfer of property — an indirect tax requiring no apportionment — upheld since Knowlton v. Moore (1900). Heir and transferee liability is ordinary transferee liability under §6901. Neither is at risk.
Where the exposure is
The annual mandatory prepayment, measured by current wealth, invites recharacterization — substance over form — as an unapportioned direct tax on property. Moore v. United States (2024) upheld attribution of realized entity income but pointedly declined to bless anything resembling a wealth tax, and four justices signaled that realization matters. The Accord scores a court striking the annual mandatory feature as a genuine risk, not a remote one.
The three hardenings
1. A true withholding regime by statute. Every prepaid dollar credits dollar-for-dollar against the estate tax; a final true-up at death exhausts any excess against the remaining transfer settlement — capital-gains-at-death first, then the heirs' accession tax — and refunds a surviving remainder without interest. Every prepaid dollar is thus either credited against an accruing liability or returned; withholding against accruing excises is far more defensible than a freestanding annual tax.
2. Severability with a named fallback. If the annual feature is enjoined, the statute automatically activates deemed realization at death plus carryover basis — a realization event exists (Moore-safe), and the debt-retirement math survives the injunction.
3. Honest scoring of the risk. The published scoring carries a conservative scenario in which prepayment revenue is enjoined for Years 1–5 (the severability fallback carrying the load). Secondary hardenings: the whistleblower bounty sits at 30% — the top of the IRS band, not above it — and enforcement damages are civil-first, with criminal referral reserved for willful concealment (post-Timbs Excessive Fines discipline).
Full memorandum in preparation (v10.11 stub, 2026-07-09). Mechanism details: /estate-prepayment · statutory language.