Estate tax portability election requires filing a full Form 706 even when no estate tax is owed, and errors are permanently fatal

What: When the first spouse dies with an estate below the federal exemption ($13.99 million in 2025), no estate tax is owed — but to transfer the deceased spouse's unused exemption (DSUE) to the surviving spouse, the executor must file a complete and properly prepared Form 706 estate tax return within five years of death (per Revenue Procedure 2022-32). The form requires full asset inventories, appraisals, and detailed schedules even though the estate owes nothing. If the form is filed late, filed incompletely, or contains valuation estimates instead of actual appraisals, the portability election is permanently lost — and the surviving spouse's estate loses up to $13.99 million in exemption. Why it matters: Many families with estates well below the exemption do not hire estate attorneys or file Form 706 because they believe (correctly) that no tax is owed — so what? Without the portability election, the surviving spouse's estate can only use their own $13.99 million exemption, not the combined $27.98 million — so what? If the exemption amount drops (which Congress may allow via sunset or reduction), the lost portability could mean millions in estate tax at the second death — so what? The Tax Court case Estate of Rowland v. Commissioner (2025) showed that an improperly prepared Form 706 filed within the deadline was still rejected, costing the family $1.5 million in additional estate taxes — so what? This means the filing must be not just timely but substantively perfect, requiring professional appraisals of every asset including real estate, closely held business interests, and personal property — an expense of $5,000-25,000 for an estate that owes zero tax. Structural root cause: The portability election was designed as an administrative simplification (replacing complex credit shelter trusts), but Congress conditioned it on filing the same 30+ page Form 706 required for taxable estates. There is no simplified portability-only form, and the IRS interprets 'complete and properly prepared' strictly — estimates, omissions, or informal valuations invalidate the election entirely.