Estate Tax Portability: What Married Couples Should Know

Federal Estate tax rules currently provide historically high exemption amounts, which may lead many families to assume estate tax planning is no longer necessary. However, Certain elections made after a spouse's death can still have significant implications for long-term estate planning.

One such rule involves the portability of the federal estate tax exemption, which may allow a surviving spouse to use a deceased spouse's unused exemption amount. Understanding how portability works and the filing requirements associated with it can help families better understand how estate tax rules may apply in the future.

Understanding the Federal Estate and Gift Tax Exemption

Federal law provides a unified estate and gift tax exemption that allows individuals to transfer a certain amount of assets without a federal estate or gift tax. According to current law, the exemption amount for 2026 is approximately $15 million per individual, or about $30 million for a married couple if both spouses' exemptions are available.

Amounts transferred above the exemption threshold may be subject to federal estate tax at graduated rates that can reach as high as 40 percent.

Because the exemption is relatively high, many families may conclude that federal estate taxes are unlikely to affect them. However, certain planning considerations particularly for married couples may still warrant attention.

What is the Estate Tax Portability Election?

Portability refers to a rule that allows a surviving spouse to use any unused portion of a deceased spouse's estate tax exemption.

When the first spouse passes away, the unused exemption does not automatically transfer to the surviving spouse. Instead, the executor of the deceased spouse's estate must make a portability election.

If the election is made properly, the surviving spouse may be able to add the unused exemption to their own exemption amount. This can increase the total amount that may ultimately be transferred to heirs without federal estate tax.

For example, if one spouse dies having used little or none of their exemption, the surviving spouse may potentially have access to a larger combined exemption.

Why the Portability Election May Matter

Although the current exemption is high, several factors may affect estate tax exposure over time:

• Changes in tax legislation

• Investment growth increasing estate values

• Inheritances or business appreciation

• Real estate or concentrated investment positions

In some situations, a surviving spouse’s estate could grow significantly after the first spouse’s death. If the unused exemption from the first spouse was preserved through portability, the surviving spouse may have access to additional estate tax protection.

Without the election, the unused exemption may be permanently lost.

Filing Requirements for Portability

To elect portability, the executor of the deceased spouse’s estate generally must file IRS Form 706 (United States Estate Tax Return).

This filing requirement applies even if the estate is below the threshold that would otherwise require an estate tax return.

The standard deadline for filing Form 706 is typically nine months after the date of death, although an automatic six-month extension may be available.

In cases where an estate is not otherwise required to file a return, the IRS may allow a simplified filing process when the return is submitted solely to elect portability.

However, the election generally must be made within the allowable timeframe in order to preserve the unused exemption.

When Portability Is Not Available

There are certain limitations to portability that may be relevant in planning discussions.

For example:

• Portability generally applies only when the surviving spouse is a U.S. citizen.

• Only the unused exemption from the most recently deceased spouse may be transferred.

These rules are intended to prevent the accumulation of multiple unused exemptions over time.

Potential Consequences of Missing the Filing Deadline

Failure to file the required estate tax return in order to elect portability may result in the loss of the deceased spouse’s unused exemption.

In some cases, estates have faced significant tax liabilities when a portability election was not properly completed or filed within the permitted timeframe.

Although each situation is unique, the example underscores how administrative requirements such as filing a return even when no tax is due can still play an important role in estate planning outcomes.

Planning Considerations for Married Couples

While many estates fall well below the federal estate tax exemption, portability may still be relevant for certain families.

Situations where portability may be worth reviewing include:

• Married couples with significant investment or real estate holdings

• Families expecting long-term asset growth

• Business owners whose company value may increase over time

• Individuals who may inherit additional assets in the future

Estate planning often involves considering not only current asset levels, but also how circumstances may evolve over time.

Final Thoughts

Today’s federal estate tax exemption levels may reduce the number of estates subject to federal estate tax. However, planning decisions made after the death of a spouse such as electing portability can still affect long-term estate outcomes.

Understanding how the portability election works and the filing requirements associated with it can help families stay informed about how estate tax rules may apply within their broader financial planning framework.

Coordinating financial, tax, and estate considerations often requires collaboration between financial professionals, tax advisors, and legal counsel. Understanding how these areas interact can help individuals and families make more informed planning decisions.

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