The exemption is permanent. Keeping the other spouse's isn't automatic.
OBBBA made the $15M / $30M federal exemption permanent. But the surviving spouse keeps the first spouse's unused exemption only if a Form 706 is filed to elect portability — even when no tax is due at the first death. That return is the thing most often missed.
1.What was the first spouse's estate value at the first death?
2.How much federal exemption had the first spouse already used (lifetime gifts, prior planning)?
Most couples leave everything to each other, which uses none of the first spouse's exemption → enter $0.
3.What is the surviving spouse's own estate expected to be at the second death?
4.Which state do you live in?
This is a simplified, educational estimate — not tax or legal advice, and not an estate plan. The DSUE election is made on a timely-filed Form 706, and the filing deadline is strict (generally about nine months after the first death, extendable to fifteen; late-portability relief may be available in some cases). Estate planning is the practice of law — work with a qualified estate attorney and tax advisor before acting.