Detailed affidavit document for estate due diligence
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Estate & Probate8 min read

What Is an Affidavit of Due Diligence and When Is It Required?

By Juan Lozano|Published March 30, 2026

An affidavit of due diligence is a legal document in which someone swears they have made reasonable efforts to locate and notify the heirs or beneficiaries of a deceased person's estate. In New York's Surrogate's Court proceedings, an affidavit of due diligence may be required to prove that notice was properly provided to all interested parties before the court issues final orders or closes an estate.

This requirement exists to protect the rights of all heirs and interested parties. Before an estate is finalized and assets distributed, the law requires that everyone who might have an interest in the estate be notified. The affidavit of due diligence documents these efforts. Understanding when this affidavit is required and how to prepare it properly is important for executors, administrators, and the professionals who guide them through the process.

What Is an Affidavit of Due Diligence and Its Purpose

An affidavit of due diligence is a sworn statement documenting the reasonable efforts made to locate and notify heirs, beneficiaries, or other interested parties in an estate. The affiant swears under oath that they've made diligent, good-faith efforts to identify and contact all persons who might have an interest in the estate. The affidavit provides proof to the Surrogate's Court that proper notice was attempted.

The legal purpose of the affidavit of due diligence is to ensure that no one entitled to notice is overlooked or deliberately excluded from the estate administration process. New York law requires that interested parties be notified before certain actions occur—like closing an estate, distributing assets, or having a fiduciary removed. The affidavit of due diligence demonstrates that the executor or administrator complied with notice requirements.

While notice is often accomplished through publication in a newspaper and service on known heirs, sometimes the executor or administrator needs to locate unknown or missing heirs. The affidavit of due diligence shows the steps taken to find these people—searches for people, efforts to contact relatives, attempts to locate former addresses, and similar efforts.

When an Affidavit of Due Diligence Is Required in New York

An affidavit of due diligence is required in several Surrogate's Court situations. Most commonly, it's required when the executor or administrator needs to locate missing heirs or beneficiaries. For example, if the deceased had children from a previous relationship and the executor doesn't know where they are, an affidavit of due diligence documents the efforts to find them.

Under SCPA 1404, an affidavit of due diligence is required when the executor has reason to believe there may be unknown creditors or claimants. The executor must show that they've published notice and made reasonable efforts to notify potential claimants. The affidavit documents these efforts.

Additionally, when closing an estate, the Surrogate may require an affidavit of due diligence to confirm that all interested parties were properly notified and given the opportunity to contest the estate's administration. The court wants assurance that the process has been fair and transparent.

An affidavit of due diligence may also be required in situations involving: removal of an executor or administrator, settlement of estate disputes, or distribution of assets before full estate closure. Whenever the court wants to ensure that all interested parties have been notified and given the opportunity to participate, the affidavit may be requested.

What Constitutes Reasonable Due Diligence

The law doesn't require the executor or administrator to find every possible heir or beneficiary, only that they exercise reasonable diligence. "Reasonable due diligence" means making good-faith, thorough efforts that an ordinarily prudent person would make under similar circumstances. This is an objective standard applied by the court.

Examples of reasonable due diligence efforts include: searching property records and tax records for current addresses; contacting known relatives and asking for information; searching public databases and online people-finder services; sending letters to last-known addresses; attempting to contact employers; checking with neighbors or community organizations; and reviewing the deceased's personal papers and correspondence for clues about relatives.

The reasonableness of efforts depends on the situation. For a person who lived their entire life in New York and had a stable family, reasonable efforts might be straightforward. For someone who moved frequently, traveled extensively, or had a complex or estranged family situation, more extensive efforts might be reasonable. Courts generally view the executor's efforts fairly, recognizing that some people are simply impossible to locate.

Preparing the Affidavit: What Information to Include

An effective affidavit of due diligence includes specific details about the steps taken. The affiant (typically the executor or administrator) should describe: when they began searching for the person, what methods they used, what results they obtained, and when they finally determined that the person couldn't be located.

The affidavit should include: dates of letters sent and to what addresses; names and dates of contacts with relatives or acquaintances; results of searches in specific databases or resources; copies of published notices sent out; and explanations of why certain searches were unsuccessful. Supporting documents—copies of letters sent, search results, published notices—should be attached as exhibits.

The affidavit must be signed before a notary public, establishing that the statements are made under oath and subject to penalties of perjury. The affiant should be specific about their personal knowledge and involvement in the search efforts. Vague affidavits that say "reasonable efforts were made" without details are less persuasive than those with specific information.

Situations Where Due Diligence May Be Challenged

A court may reject an affidavit of due diligence if it finds that efforts were insufficient. This sometimes happens when an heir comes forward after an estate is closed, claiming they were never notified. If the court determines that reasonable due diligence would have located that person, it may reopen the estate or hold the executor liable.

Additionally, if the executor deliberately avoids finding certain heirs to benefit other beneficiaries, this constitutes breach of fiduciary duty. If an heir can prove that the executor acted in bad faith or failed to make reasonable efforts, the court may surcharge the executor (require them to pay the estate for losses) or remove them.

Courts expect reasonable efforts, not perfect results. However, they also expect the executor to act honestly and in the estate's interest. If someone with current information about missing heirs provides that information to the executor and the executor fails to act, this suggests a lack of due diligence.

Best Practices for Ensuring Adequate Due Diligence

The best practice is to document every effort made to locate and notify heirs. Keep detailed notes of dates, times, methods, and results. Save copies of all published notices, letters sent, and search results. If you contact relatives, document what was said and what information they provided.

Consider using professional search services if standard efforts fail to locate someone. Private investigators, genealogy services, and online databases can help locate people who have moved or disappeared. Using professional services demonstrates reasonable, thorough efforts to the court.

Keep good records throughout the estate administration process, not just at the end. If you need to prepare an affidavit of due diligence, detailed contemporaneous records are much more persuasive than trying to reconstruct efforts from memory months later. Document everything, and you'll be prepared if the court requires an affidavit.

How Keystone Pinnacle Can Help

Whether you're navigating an estate property sale, exploring investment opportunities, or need guidance through a complex real estate transaction, Keystone Pinnacle Property Advisors is here to help. Our team specializes in guiding families through the real estate aspects of estate settlement throughout Brooklyn, Queens, Nassau County, and the greater New York area.

Contact us today for a free consultation, or call (516) 703-6942 to speak with an advisor.

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