Portability Election Calculator
2026 exclusion · reviewed September 6, 2026
Shows what filing an estate tax return at the first spouse's death, to carry over their unused exclusion, is worth to the survivor. AboutLess
In plain words. Each person can leave a large amount free of federal estate tax. When the first spouse dies and leaves everything to the survivor, none of that allowance is used. The law lets the survivor add it to their own, doubling what they can leave, but only if the first estate files an estate tax return and asks for it, even when no tax is due. This tool takes what the first spouse left to others and the survivor's expected estate, and shows the federal tax with and without the election.
Why it matters. The filing happens when the estate looks too small to bother, and the value shows up years later when the survivor's estate has grown. Skip it and the allowance is gone. Illinois has no version of this, which is why Illinois couples still plan differently.
An example. The first spouse leaves everything to the survivor. If the survivor later dies with $20 million, the federal tax is about $2 million without the election and nothing with it. The Illinois tax is the same either way.
Where it stops. It uses today's exclusion, which the law can change, and treats the survivor's estate as taxed at the top rate above the allowance. Lifetime gifts, the exact return due date, and whether a trust at the first death would serve better are the attorney's questions. Everything it leaves out.
Add any large lifetime gifts reported on gift tax returns. This is the part of the first spouse's exclusion that was used up. Often zero.
A best guess, in today's dollars. The election's value is measured against this number.
- Unused exclusion the election carries over
- $15 million
- The $15 million federal exclusion less what the first spouse's estate used
- Amount the surviving spouse can leave free of federal tax, with the election
- $30 million
- $15 million without it. Tax of 40% on anything above.
- Illinois estate tax on the surviving spouse's estate
- $2,298,965
- Illinois does not allow the carry-over, so this is the same either way
The election is made on a full federal estate tax return for the first spouse, Form 706, due nine months after the death. If no return was otherwise required, a simplified late filing is allowed within 5 years. The return costs an appraisal and a filing at a moment when the estate seems too small to matter. But the surviving spouse's estate can grow, the law can cut the exclusion, and the return is the only way to keep the option.
This follows the federal portability rules and the simplified late-election procedure, using the 2026 exclusion and the Illinois estate tax computation. It taxes the surviving spouse's estate at the top rate above the exclusion, with no deductions, credits, or growth in the exclusion, and it leaves out a later remarriage (only the most recent deceased spouse's unused exclusion counts), gifts made after the death, and any other state's estate tax. Educational, not advice.
This is a simplified model, not your actual tax return or plan. It only knows what you type in, leaves out rules that may apply to you, and cannot weigh the other facts and trade-offs a real decision depends on. Before you act, talk with a professional who knows your whole situation.
Educational only, not investment, tax, or legal advice. Results are hypothetical estimates that vary with each use and over time and are not guaranteed accurate or complete. Using this tool creates no client relationship with Considerate Capital, and the site that linked here is not affiliated with it. By using it you agree to the tool terms.