A demand for preservation of evidence is a letter that tells the other side of a potential lawsuit to safeguard specific documents, electronic data, and physical items. To write one, identify yourself and the recipient, describe the dispute, state plainly that you are contemplating litigation, list the categories of evidence you want preserved with as much specificity as you can manage, warn that destroying evidence can trigger court sanctions, and send it in a way that proves receipt. The details in each of those parts are what determine whether a court later treats your letter as an enforceable demand or an easily brushed-aside formality.
Send It as Soon as Litigation Looks Likely
The legal duty to preserve evidence attaches the moment litigation becomes reasonably foreseeable. You don’t need a filed case or even a firm decision to sue. The duty can arise from a demand letter, a workplace complaint, retaining a lawyer about a dispute, or any event that would put a reasonable person on notice that a lawsuit is likely.
Your letter doesn’t create that duty, but it eliminates any argument that the recipient didn’t know a lawsuit was coming. It pins down the exact moment they were put on notice, which matters if evidence later goes missing. Timing is urgent for a practical reason too: automated systems overwrite backups, employees delete old messages, and surveillance footage loops on fixed cycles. Every day you wait is a day evidence can vanish through routine operations.
The Five Parts of the Letter
Courts look at whether your letter was specific enough to put the recipient on reasonable notice. Vague requests weaken your position later. A workable letter has five sections, in this order.
Identify the Parties
Say who is sending the letter and who is receiving it. If you’re writing to a corporation, address the letter to its general counsel or a senior executive such as the CEO or CFO. If the other side already has a lawyer, send it to the attorney. Include your full name, contact information, and the capacity in which you’re writing, such as “injured party” or “former employee.”
Describe the Dispute
Give enough detail that the recipient can identify the relevant events. Include the date and location of the incident and a brief description of what happened. You don’t need to lay out your entire legal theory, but the recipient needs enough context to figure out which of their records are relevant.
State That Litigation Is Anticipated
Include a clear, unambiguous statement that you are contemplating legal action. Something like: “Please be advised that I am considering filing a lawsuit related to the above-described incident.” That sentence is what formally puts the recipient on notice and ties the letter to their legal obligation to preserve evidence.
List the Evidence You Want Preserved
This is the core of the letter. Be as specific as you can about the types of documents, the people whose files should be preserved, and the time period covered. Instead of asking for “all emails,” request “all emails sent or received by [Name] and [Name] between [Date] and [Date] concerning [subject matter].” Instead of “personnel records,” specify “any performance reviews, disciplinary records, or complaints related to [Name] from [Year] to present.”
Include explicit instructions about electronic preservation. Demand that the recipient suspend any document retention or auto-deletion policies, prevent backup systems from overwriting stored data, and preserve all metadata associated with relevant files. If you know the other side uses specific software or cloud platforms, name them. The more concrete your request, the harder it is for the other side to later claim they didn’t understand what to keep.
Warn About Consequences
Close by notifying the recipient that destroying, altering, or concealing any of the listed evidence may result in court sanctions. You don’t need to cite rules or case law. A straightforward statement that spoliation of evidence can lead to adverse legal consequences is enough.
What to Put on the Evidence List
Cast a wide net. Relevant material can be scattered across dozens of systems and locations, and splitting your list into electronic and physical categories helps you avoid obvious gaps.
Electronic Evidence
Digital evidence covers anything stored on computers, servers, phones, or cloud platforms: emails, text messages, direct messages on workplace platforms like Slack or Teams, social media posts, calendar entries, voicemails, and call logs. Spreadsheets, presentations, word processing files, and database records all belong here, along with digital photos, videos, and website content.
Don’t overlook metadata and system-level data. Metadata is the behind-the-scenes information attached to every file: who created it, when it was last modified, who accessed it. It can be as revealing as the document itself and is easily destroyed by routine system operations. Server logs, access records, and GPS data from company vehicles or phones are easy to forget and even easier for the other side to let disappear.
Physical Evidence
Physical evidence is anything tangible: damaged property, defective products, paper contracts, handwritten notes, maintenance logs, personnel files, or hardware from a surveillance system. In vehicle accident cases, the event data recorder (sometimes called a “black box”) stores objective crash data that overwrites after a limited number of events, making it especially time-sensitive. Whatever the item, your demand should make clear it must be kept in its current condition. Repairs, modifications, or even routine cleaning can destroy evidence and invite accusations of tampering.
How to Send It
Delivery matters almost as much as content. The goal is to create an undeniable record that the other party received your demand on a specific date.
The standard method is USPS Certified Mail with Return Receipt Requested. Certified Mail gives you a mailing receipt with a tracking number, and the Return Receipt gives you a signed card confirming who accepted delivery and when. As of January 2026, the Certified Mail fee is $5.30 per item, the physical Return Receipt (PS Form 3811) costs $4.40, and an electronic Return Receipt costs $2.82, all on top of standard first-class postage of $0.78.1United States Postal Service. USPS Notice 123 – January 2026 Price Change For a standard one-ounce letter with a physical Return Receipt, that comes to roughly $10.50 total.
Send a duplicate copy by email the same day. Email creates an instant, timestamped digital record and eliminates any “I never got it” defense. Attach the letter as a PDF so the formatting is preserved. Keep copies of everything: the letter itself, the certified mail receipt, the signed return receipt card when it comes back, and the sent email with its timestamp.
What Happens if They Destroy Evidence Anyway
When a party destroys, alters, or hides evidence after the duty to preserve has been triggered, courts call it spoliation. In federal court, Federal Rule of Civil Procedure 37(e) governs sanctions for lost electronically stored information, and the consequences get dramatically worse when the destruction was intentional.2Legal Information Institute. Federal Rules of Civil Procedure Rule 37
If the court finds that lost evidence prejudiced your case but the other side didn’t intentionally destroy it, the court can order measures to cure that prejudice, such as allowing additional discovery, requiring the spoliating party to pay your costs, or precluding certain arguments. The remedy has to be proportional to the harm.
If the court finds the other side acted with intent to deprive you of the evidence, the sanctions become severe. The judge can instruct the jury that it may presume the destroyed evidence would have been unfavorable, presume unfavorable content outright, or in the most extreme cases dismiss the spoliating party’s claims or enter default judgment against them.2Legal Information Institute. Federal Rules of Civil Procedure Rule 37
This split between negligent and intentional destruction is the whole reason your letter matters so much. Once the other side has received a written demand spelling out exactly what to keep, later destruction looks far less like an innocent mistake and far more like something done on purpose. Your letter is what turns “we didn’t know” into evidence of intent.
State courts apply their own spoliation standards, and some are more forgiving than others. A few states allow adverse inferences based on negligence rather than requiring proof of intent. If your case will be in state court, check your jurisdiction’s framework; the federal rule above applies only in federal proceedings.