To write an affidavit for court, you put facts you personally know into a numbered, first-person written statement, then sign it under oath in front of a notary public. The document carries the same weight as live testimony, and courts apply the same evidence rules to it: statements must be based on personal knowledge, must be facts rather than opinions, and must be presented in a format the court recognizes. Lying in one is perjury, punishable under federal law by up to five years in prison.1Office of the Law Revision Counsel. 18 USC 1621 – Perjury Generally
What the Document Must Contain
Courts expect a specific layout. Type the whole document in a standard, readable font at 12-point size, and work through the sections below in order.
Caption
The top of the first page identifies the court and the case. Include the full name of the court (for example, “United States District Court, Northern District of Illinois”), the names of the plaintiff and defendant, and the case number assigned by the clerk. Below the caption, center a title identifying the document and the person making the statement, such as “AFFIDAVIT OF JANE DOE.”
Opening Paragraph
The first paragraph introduces you. State your full legal name, your age, and your residential address. Some jurisdictions also expect your occupation. Follow this with a sentence confirming that you have personal knowledge of the facts and are competent to testify about them. A standard opening reads: “I, Jane Doe, am over eighteen years of age, reside at 100 Maple Drive, Springfield, and have personal knowledge of the facts stated in this affidavit.”
Numbered Factual Paragraphs
The body is a series of numbered paragraphs, each containing one distinct fact. One fact per paragraph makes it easy for the court and opposing counsel to reference specific statements. Write in the first person. Be precise about dates, times, locations, and names. Vague wording weakens the document.
Compare “I saw the defendant at the property” with “On March 15, 2025, at approximately 2:00 p.m., I saw John Smith enter the building at 500 Elm Avenue.” The second sentence can be tested; the first cannot.
Closing and Jurat
After your last numbered paragraph, add a closing statement reaffirming that everything above is true and correct. Leave a signature line with space for your handwritten signature and your printed name beneath it. Do not sign yet. Below the signature block, include the jurat, the section the notary completes. It typically reads: “Sworn to and subscribed before me this ___ day of ___, 20__,” followed by lines for the notary’s signature, printed name, commission expiration date, and seal.
Stick to What You Personally Know
The single most important rule for the content is that you can only state facts you personally witnessed, heard, or experienced. Federal Rule of Evidence 602 bars testimony from a witness who lacks personal knowledge of the matter, and the same standard applies to written statements under oath.2Legal Information Institute. Federal Rules of Evidence Rule 602 – Need for Personal Knowledge An affidavit that fails to show the basis for your knowledge can be struck entirely, leaving the party who filed it with no supporting evidence.
A workable factual statement sounds like: “On June 3, 2025, I was standing in the parking lot of 412 Oak Street and saw a white sedan run the red light at the intersection.” It tells the court where you were, when you were there, and what you observed. Compare that to “The driver was being reckless,” which is your opinion, not a fact. Worse still is “My neighbor told me the driver ran the light.” That’s hearsay, and it will get the paragraph disregarded because you didn’t see the event yourself.
As you write each paragraph, ask whether you could testify to it on a witness stand. If the answer is no because you’re relying on someone else’s account or drawing a conclusion rather than describing what happened, leave it out.
If You’re Authenticating Business Records
There is one narrow exception to the firsthand rule. A records custodian for a business or organization can submit an affidavit authenticating business documents without having personally created them. To use this exception, the affidavit must show that the records were created in the normal course of business, that the person who originally recorded the information had a duty to report it accurately, and that the records were made at or near the time of the events they describe. Courts have rejected these affidavits when the signer was never an employee of the company that generated the records or couldn’t explain the company’s recordkeeping procedures.
Signing: Notary or Unsworn Declaration
Most affidavits are notarized, but federal law gives you an alternative. Under 28 U.S.C. § 1746, an unsworn declaration carries the same legal force as a traditional notarized affidavit if it includes specific language and your signature.3Office of the Law Revision Counsel. 28 USC 1746 – Unsworn Declarations Under Penalty of Perjury If you sign within the United States, the required closing is: “I declare under penalty of perjury that the foregoing is true and correct. Executed on [date].” followed by your signature. If you sign outside the country, add “under the laws of the United States of America” after “penalty of perjury.”
This option doesn’t fit every situation. The statute excludes depositions and oaths required before a specific official other than a notary public, and it applies where federal law governs. Some state courts accept unsworn declarations under their own rules; others still require notarization. Check the procedural rules for your specific court before choosing. When in doubt, notarization is the safer path because no court rejects a properly notarized affidavit in favor of an unsworn one.
If you’re going the traditional route, do not sign the document before you reach the notary. You must sign in the notary’s physical presence. Bring the complete, unsigned affidavit and a valid government-issued photo ID. The notary will verify your identity, administer an oath or affirmation (both carry identical legal weight), watch you sign, and then complete the jurat with the date, their signature, their official seal, and their commission expiration date.
Banks, shipping stores, courthouses, and many law offices offer notary services. Nearly all states also permit remote online notarization, where you appear by live video rather than in person. The rules are the same through video: identity verification, oath, and signing in the notary’s view.
Why Affidavits Get Thrown Out
A poorly drafted affidavit can sink your case. Courts regularly strike affidavits that fail to lay a proper foundation, and once the supporting evidence is gone, so is the argument. Federal Rule of Civil Procedure 56 specifically requires that any affidavit filed in connection with summary judgment be based on personal knowledge and contain facts that would be admissible as evidence.4Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment If your affidavit contains opinions, hearsay, or statements where you haven’t shown how you personally know the facts, the opposing side will move to strike it.
When the court grants that motion, the challenged paragraphs are treated as if they don’t exist. If those were the only paragraphs supporting your position, you lose on summary judgment without reaching trial. The same applies to documents attached to the affidavit: if you can’t explain where they came from and lay a foundation for their admissibility, the court disregards them.
Technical defects also cause rejection. An affidavit missing the notary’s seal, lacking a jurat, or signed before the notary arrived may be challenged as improperly executed. Some courts allow you to correct these errors with an amended filing; not all do, and deadlines keep running while you fix mistakes.
What Happens if You Lie
Because the affidavit is sworn testimony, a knowing falsehood in one is perjury. Federal law punishes anyone who willfully states something they don’t believe to be true in a sworn affidavit or an unsworn declaration under penalty of perjury with up to five years in prison, a fine, or both.1Office of the Law Revision Counsel. 18 USC 1621 – Perjury Generally The statute reaches “material” statements, meaning falsehoods that matter to the proceeding. A trivial error, such as getting a date slightly wrong, is unlikely to trigger prosecution. Deliberately misrepresenting facts that affect the outcome of a case can.
Courts also have civil tools. They can dismiss claims or defenses supported by fraudulent evidence, award attorney fees to the other side, and impose monetary penalties. If you realize after signing that something in your affidavit is inaccurate, file a corrected or supplemental affidavit immediately rather than waiting to see whether anyone catches it.
Filing and Serving the Finished Affidavit
After the affidavit is signed and notarized (or properly executed as an unsworn declaration), it needs to reach both the court and every other party in the case. Filing means delivering the original to the court clerk, who stamps it and adds it to the official case file. Many courts accept electronic filing, which is faster and creates an automatic timestamp.
Serving means providing copies to opposing parties. Methods depend on your court’s rules and commonly include first-class mail, hand delivery, and electronic service through the court’s filing system. Some situations require a professional process server.
After service, file a proof of service (sometimes called a certificate of service) with the court. This short document confirms who was served, when, and by what method. Without it, the court has no record that the other side received the document, and a judge may decline to consider the affidavit until proof of service is on file. Watch the deadlines. Filing rules specify how far in advance of a hearing your affidavit and proof of service must be submitted, and missing those deadlines can mean the evidence is never considered.