Filing a federal estate tax return can be complex, but having a clear roadmap makes the process far less stressful. This Form 706 filing checklist 2025 is designed to help executors, estate planners, and families understand the critical steps, deadlines, and documentation required when representing a U.S. estate. From the Form 706 deadline and the option to request a 6-month filing extension with Form 4768, to making a portability election for a surviving spouse and calculating the Deceased Spousal Unused Exclusion (DSUE), this guide explains what you need to prepare before submitting Form 706.

Whether you are handling an estate for the first time or working with a professional advisor, this checklist will help you stay organized and avoid costly errors.

TLDR:

Who must file: Estates for decedents in 2025 whose gross estate plus adjusted taxable gifts exceed $13.99 million (the basic exclusion), or any estate electing portability for a surviving spouse.

Deadline: Form 706 is due 9 months after death, with the option to request a 6-month filing extension using Form 4768. (Note that payment extensions are separate and not automatic.)

Portability (DSUE): To transfer unused exclusion to a surviving spouse, executors must make a DSUE portability election by filing a complete Form 706 on time. Late elections may still be possible within 5 years under Rev. Proc. 2022-32.

Who Must File Form 706 in 2025?

Estates of U.S. decedents with a gross estate (including property interests, life insurance, and certain prior transfers) plus adjusted taxable gifts exceeding $13,990,000 must file Form 706 for deaths occurring in 2025.

Estates Below the $13.99M Threshold

Even if no estate tax is due, an executor may still need to file Form 706 to make a portability election for the Deceased Spousal Unused Exclusion (DSUE). Filing on time ensures the surviving spouse can carry forward the unused exclusion and shelter more assets from future estate tax.

Why this matters: Without filing, the DSUE cannot be transferred, and the surviving spouse may lose significant estate tax protection.

Canadians and Other Nonresidents

For Canadians and other foreign individuals, U.S. estate tax may apply to U.S. situs assets if their value exceeds $60,000. In these cases, executors generally must file Form 706-NA instead of Form 706.

Checklist: What to Include and Consider

  • Determine Gross Estate Value
    • Add up all worldwide property interests, adjusted taxable gifts, and other includible assets.
    • Don’t forget life insurance, joint property, and certain trust interests.
  • Check the $13.99M Exemption
  • Complete All Schedules and Attachments
    • Property appraisals and valuation details
    • Deductions for debts, funeral expenses, administration costs, marital and charitable transfers
    • Gift history, including Form 709 copies
  • Portability Election (DSUE)
    • Complete Section A and Part VI of Form 706 to elect portability.
    • If opting out, check the appropriate box.
  • Key Filing Deadlines for 2025
    • Form 706 is due 9 months after the date of death (e.g., a death on March 1 makes the due date December 1).
    • File Form 4768 before the original deadline to secure an automatic 6-month filing extension.
    • Payment of estate tax is also due at 9 months, and late payment may trigger penalties and interest.

Deadlines & Extensions (What to Calendar)

Estate Tax Return Deadline

The Form 706 estate tax return is due within 9 months of the decedent’s death. For example, if the death occurred on March 1, the final due date to submit the return is December 1.

Requesting an Automatic Extension

Executors may apply for an automatic 6-month filing extension for Form 706 by submitting IRS Form 4768 before the original deadline. This provides additional time to complete the return but does not extend the deadline for paying any estate tax owed.

Extending Time to Pay Estate Tax

While filing Form 4768 covers the return filing, the estate tax payment deadline remains at 9 months. To delay payment, executors can apply for relief under Internal Revenue Code Section 6161, using Form 4768 to request extra time. Common reasons include limited estate liquidity or unresolved valuations.

IRS Review and Accrued Interest

Requests for payment extensions must be filed promptly and require strong supporting documentation. The IRS reviews each application individually, and interest on unpaid estate taxes will continue to accrue during the extended period, even if the extension is granted.

Portability & DSUE—How to Elect (and Fix It If Missed)

Making the Portability Election

Electing portability is not automatic. The executor must file a timely and complete Form 706 estate tax return and complete the sections related to Portability and the Deceased Spousal Unused Exclusion (DSUE) in order to transfer any unused exclusion amount to the surviving spouse.

The election must be made by filing Form 706 within 9 months of the decedent’s death, or by the last day of any approved extension. For estates required to file Form 706 because they exceed the exemption amount, the election is generally deemed made unless the executor chooses to opt out.

Late Portability—The Five-Year Rule

For estates not otherwise required to file, missing the deadline does not always mean losing portability. Under Revenue Procedure 2022-32, executors may still make a simplified late election.

To qualify, the executor must file Form 706 within 5 years of the date of death, clearly noting on the top of the return:
 “FILED PURSUANT TO REV. PROC. 2022-32 TO ELECT PORTABILITY UNDER SECTION 2010(c)(5)(A).”

This option applies only to estates below the filing threshold that want to preserve the DSUE for the surviving spouse.

Practical Tips for Executors

  • Verify surviving spouse’s details – Double-check marital status, names, and Social Security numbers before filing.
  • Maintain complete gift records – Keep copies of prior Form 709 gift tax returns to accurately calculate the DSUE and document lifetime transfers.
  • Follow DSUE calculation rules – Use the instructions in Part VI of Form 706 to compute the DSUE correctly. Incomplete or incorrect records can lead to errors that jeopardize the election.

Filing promptly—and taking advantage of the five-year late election if portability was overlooked—ensures the surviving spouse can benefit from the unused exemption to reduce transfer taxes on future gifts or their own estate.

Form 706 Documents & Valuations—Your Working List

Proper documentation is critical for a complete and accurate Form 706 filing. Executors should begin assembling these records early to avoid last-minute delays and to support fair market valuations across all categories of estate property.

Vital Records

  • Certified death certificate
  • The decedent’s last will and testament and any codicils
  • All trust agreements, including QTIP trust instruments and QDOT trusts if applicable

Asset Evidence at Date of Death

  • Bank statements and brokerage account records covering the date of death
  • IRS Form 712 for each life insurance policy (including those owned by others where the decedent was the insured)
  • Retirement account statements such as IRA, 401(k), or pension accounts

Appraisals

  • Independent written real estate appraisals
  • Professional valuations for artwork, jewelry, vehicles, collectibles, and personal effects
  • Detailed business valuations for closely held corporations, LLCs, and partnership interests

Business Documentation

  • Capitalization tables (cap tables)
  • Shareholder agreements or partnership agreements
  • Buy-sell agreements
  • Business financial statements for the past five years

Liabilities & Expenses

  • Documentation of all mortgages, promissory notes, and outstanding debts
  • Records of real estate taxes due, unpaid bills, and outstanding loans
  • Invoices for funeral expenses and administrative costs

Gifts & Elections

  • All prior Form 709 gift tax returns with supporting schedules
  • Documentation of gift-splitting elections
  • Details of generation-skipping transfer (GST) allocations

International Items (If Applicable)

  • Documentation of foreign assets and their values
  • Proof of beneficiary citizenship or residency status
  • Estate tax treaty forms or supporting documentation if cross-border rules apply

Maintaining well-organized records and professional valuation reports for each of these categories is essential to ensure a complete, accurate, and compliant estate tax return under Form 706.

Common Mistakes (and How to Avoid Them)

Frequent Errors in Form 706 Filing

  • Missing critical deadlines – Executors often overlook the 9-month estate tax filing deadline or fail to submit Form 4768 to obtain the automatic 6-month filing extension. Always calendar the due date from the date of death and submit Form 4768 on time to remain compliant.
  • Filing an incomplete or inaccurate return – Portability elections can be denied if the return is not properly prepared. Using estimates instead of formal appraisals, omitting Form 712 for life insurance, or failing to itemize assets can all trigger problems. The Estate of Rowland case is a reminder that a return must be both timely and complete to preserve portability.
  • Not filing when below the threshold – Many executors skip filing when the estate value is under the exemption limit. However, filing a portability-only Form 706 preserves the Deceased Spousal Unused Exclusion (DSUE) for the surviving spouse. If missed, use the five-year late portability election under Rev. Proc. 2022-32 to fix it.
  • Overlooking QDOT requirements – When the surviving spouse is not a U.S. citizen, a Qualified Domestic Trust (QDOT) must be established to qualify for the marital deduction. Portability benefits are limited and may be reduced based on the value or distribution of QDOT property.

How to Avoid These Errors

  • Track key filing dates early – Set reminders to file Form 706 within nine months, or file Form 4768 before the deadline to extend the filing period while completing appraisals and required schedules.
  • Provide detailed documentation – Prepare a complete and properly itemized estate tax return with professional appraisals, Form 712 for insurance, and accurate fair market values. Avoid relying on estimates unless the IRS explicitly allows relaxed reporting for specific asset categories.
  • Preserve DSUE for the surviving spouse – File a portability-only Form 706 even if the estate is below the exemption threshold. If missed, file a late portability election within five years under Rev. Proc. 2022-32.
  • Plan for non-citizen surviving spouses – Review QDOT trust requirements early in the process. Make the necessary QDOT election on Form 706, and note that DSUE usage is limited while the trust remains active.

Conclusion

Filing Form 706 accurately and on time is more than just a compliance task—it’s an opportunity to protect the surviving spouse’s financial future and preserve valuable tax benefits. Whether you are calculating the Deceased Spousal Unused Exclusion (DSUE), preparing appraisals, or managing multi-jurisdictional assets, attention to detail matters at every step.

With deadlines, valuation standards, and portability rules evolving under U.S. estate tax law, working with experienced professionals ensures your filing is correct the first time and that no available exclusions or deductions are lost.

Form 706 filing checklist 2025 for estate tax return and DSUE portability planning
Learn what documents and deadlines are required to file Form 706 accurately and preserve DSUE portability for a surviving spouse.

Get Expert Help with Form 706 and DSUE Planning

TMP’s cross-border tax team assists clients across the U.S. and Canada with Form 706 estate tax filings, DSUE portability elections, and late election relief under Rev. Proc. 2022-32. Our advisors can also help evaluate QDOT requirements for non-citizen spouses and coordinate valuations, trust documentation, and IRS correspondence on your behalf.

Plan with confidence. Learn more about our U.S. Estate Tax Services or connect with our Estate Planning Advisors to discuss your situation.