Form 706 estate tax returns have a well-earned reputation as complex, time-consuming, and expensive filings, often requiring intrusive valuations, many attachments, and careful navigation of technical tax rules. As a result, estate administrators, high-net-worth families, and their advisors routinely weigh the costs of compliance against the perceived benefit of filing, particularly when no federal estate tax is due. Yet that analysis often overlooks a critical point: For many estates, the most expensive Form 706 mistake is not making an error on the return but failing to file one at all.
Beyond reporting and paying estate tax, a properly filed Form 706 can preserve portability, limit future IRS valuation disputes, document critical tax elections, and create a comprehensive financial record that may benefit the estate and its beneficiaries for years, or even generations, to come.
Locking in portability: insurance against uncertainty
For married couples, a key reason to file Form 706, when not otherwise required, is to elect “portability” of a deceased spouse’s unused estate tax exemption. Portability generally allows a surviving spouse to use the deceased spouse’s unused federal estate tax exemption (DSUE) against their own gifting or ultimate gross estate. Portability is not automatic, however. The portability election generally requires a timely filed Form 706, though a late filing for portability may be permissible if a filing requirement for Form 706 does not otherwise exist.
Preserving a deceased spouse’s unused estate tax exemption can create significant value given that investment returns may increase the surviving spouse’s net worth, future legislation may reduce the federal lifetime exemption amount, and inheritances or other life events may increase the surviving spouse’s gross estate value. If a Form 706 is not filed for portability, a surviving spouse’s estate may end up paying estate tax unnecessarily.
A Form 706 can function like an estate tax “insurance policy.” Filing this return can give the surviving spouse and their advisors a locked-in planning tool they can rely on later, rather than having to deal with the uncertainty of the future and mitigate the odds of a potential future-taxable estate.
Establishing asset values and starting the statute of limitations
Filing an unabridged Form 706 documents how reported asset fair-market-values were derived and limits the amount of time the IRS can challenge the values reported (assuming the assets reported on the return meet the IRS adequate disclosure standards). Without adequate disclosure on Form 706, the IRS can challenge a valuation position at any time in the future, with no statute of limitations. This is particularly salient, because the fair-market-value of a decedent’s assets on date-of-passing serve as the starting point for asset basis reported on future income tax returns.
For example, assume a decedent owned a business. The estate administrator may find they have a reasonable position to value the business below the federal estate tax exemption and pay no estate tax. If that valuation is adequately disclosed on a filed Form 706, with the supporting valuation attached, the IRS generally has three years to challenge the reported value.
Had the estate administrator in this example not filed Form 706, the IRS could challenge asset basis reported on an heir’s income tax return — potentially months, years, or even decades after a decedent has passed away. The IRS could also, depending on the magnitude of the claimed difference, assess estate or other transfer tax, penalties, and interest years later, potentially creating a significant, catastrophic, and unexpected liability.
IRS valuation adjustments can also create difficult family dynamics. Let’s say a decedent's estate plan intended a 50/50 split between two children, but one inherited a closely held asset while the other received marketable securities as part of an equalization strategy. A subsequent IRS determination that the closely held asset was undervalued could alter the economics of the distribution. In that situation, the child who received the securities may view the outcome as inequitable.
A complete Form 706 filed per IRS specification can give an estate administrator and the estate’s heirs something equally valuable to immediate economic benefit: closure.
Securing tax benefits for generations to come
The Generation-Skipping Transfer (GST) tax is an additional federal transfer tax designed to prevent wealth from avoiding the gift or estate tax by skipping a generation, such as when assets pass to grandchildren, more remote descendants, or certain long-term trusts. Each person has a GST exemption that can be allocated to protect certain transfers from GST tax.
Families often use trusts to benefit children, grandchildren, and more remote descendants, (often grouped into the term “skip persons”), and those structures may require intentional decisions about GST tax exemption.
A trust’s GST tax character (that is, whether future distributions to skip persons could be subject to GST tax) is determined by how GST exemption is allocated to the trust. For trusts created at death, the Treasury-prescribed automatic allocation rules apply unless the estate administrator elects to override those automatic allocation rules. These elections are made on Schedule R of Form 706 and should be supported by appropriate attachments to the return. If an overriding election is not made, unintended, negative consequences can potentially occur.
For example, depending on a trust's terms, the automatic allocation rules may fail to allocate GST exemption to a trust intended to benefit skip persons, potentially resulting in future GST tax liability that could otherwise have been avoided.
Furthermore, GST tax elections are especially important because, unlike the estate tax exemption, GST exemption is not portable to a surviving spouse (even if a Form 706 is filed for portability reasons). If an estate plan includes ongoing, multi-generational trusts, it is always worth considering GST tax impact and the potential for affirmative or overriding elections before finalizing an administration.
Because GST exemption is not portable and elections generally must be made on a timely filed Form 706, a decision not to file can permanently limit a family's ability to optimize multigenerational wealth transfers.
A final personal balance sheet
A Form 706 can also serve as a comprehensive financial record for an estate administrator, professional advisors, and an estate’s heirs. Estate tax returns can be thousands of pages long, due to information required to be gathered and attached. Some of the documentation often attached includes, business valuations, jewelry/collectible appraisals, investment portfolio value reports, bank balance statements, real estate appraisals, trust documents, and more. Organizing that information on one filing creates a practical reference point for the family and its advisors.
By filing Form 706, an estate administrator creates a centralized record of the estate’s assets, liabilities, ownership structure, and reported values. That record can support future income tax basis reporting, trust administration, and advisor or heir questions, while reducing the risk of future issues caused by lost records, incomplete documentation, or uncertainty about what the decedent owned at death. A Form 706 filing can save heirs, estate administrators, and advisors significant time, expense, and frustration down the line.
A filing that is well worth the effort
Filing Form 706 is often viewed as a tax compliance exercise. In reality, it can be a planning document that preserves exemption for future use, establishes valuation positions while starting the IRS challenge clock, documents GST elections, and creates a permanent financial record for the future.
When evaluating an estate settlement strategy, families should consider not only whether Form 706 is required, but whether the long-term, non-tax-payment-related advantages make filing a prudent decision.
FAQs
When is a Form 706 due?
In general, federal estate tax returns are due nine months after a decedent’s date-of-death, though an extension may be available.
When is a Form 706 required?
An estate tax return is generally required when the total gross estate plus adjusted taxable gifts exceeds the lifetime exemption amount. The threshold changes annually.
How should I file a Form 706?
Form 706 is a highly technical tax return with consequences that can affect planning for generations. Omissions, improper elections, or inadequate disclosure can limit future tax benefits, leave valuation positions open to IRS challenge, compromise portability to a surviving spouse, and/or interfere with GST tax planning. Families, estate administrators, and their advisors should not approach the filing casually. For affluent families, an estate tax return can be a strategic planning tool that preserves flexibility, protects wealth, and creates certainty for future generations.
How we can help
Mowery & Schoenfeld brings deep technical expertise to estate tax filings, as well as complex estate planning matters. Learn more about our estate, gift, and trust planning services