To make a sworn affidavit, write a signed statement of facts you know firsthand, lay it out with a case caption and numbered paragraphs, close it with an oath or a declaration under penalty of perjury, and sign it in front of a notary (unless you’re in a federal proceeding, where an unsworn declaration will do). Get the format wrong or slip in something you don’t personally know, and a court can strike the whole document from the record.
What Belongs in the Affidavit
Every affidavit has three parts: identifying information at the top, the facts in the middle, and the oath and signature block at the bottom.
The top carries the case caption — the full name of the court, the parties (for example, “Smith v. Jones”), and the case number. If the case already exists, copy this information directly from another filing so it matches exactly. Below the caption, give your full legal name and current address. Some courts also want your occupation.
Then comes the substance. Every fact must come from your own direct, personal knowledge: what you saw, heard, did, or experienced yourself.1Legal Information Institute. Federal Rules of Evidence Rule 602 – Need for Personal Knowledge You cannot pass along what someone else told you, guess at what probably happened, or offer legal opinions about what the facts mean. Courts enforce this strictly. Affidavits full of speculation, conclusions, or hearsay routinely get thrown out at summary judgment.2Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment
If a fact depends on a document rather than direct observation, say so plainly. “I reviewed the bank statement dated March 15, 2025, which showed a balance of $4,200” is far stronger than “The account had about $4,200 in it.”
How to Write It
Start with a centered title: AFFIDAVIT OF [YOUR FULL NAME]. Place the case caption directly below in the same format the court uses on other filings.
Open the body with a short introduction: “I, [Full Name], being duly sworn, state as follows.” Then break each fact into its own numbered paragraph. Numbering isn’t cosmetic. It lets the court, attorneys, and opposing parties reference statements by number, which matters if any part of the affidavit gets challenged. Keep each paragraph focused on one point. Arrange them chronologically when you’re telling a story; group them by topic when you’re presenting separate categories of information.
After the numbered paragraphs, add a closing statement confirming the truth of what you’ve written. In federal proceedings, the standard language is: “I declare under penalty of perjury that the foregoing is true and correct.”3Office of the Law Revision Counsel. 28 USC 1746 – Unsworn Declarations Under Penalty of Perjury Leave space below for your signature, printed name, and the date.
At the bottom, add the jurat — the block the notary completes. It usually reads “Sworn to and subscribed before me on [date] by [affiant’s name],” followed by spaces for the notary’s signature, printed name, commission expiration date, and seal. Don’t fill in any part of the jurat yourself; that’s the notary’s job.
Notarization or Declaration Under Penalty of Perjury
Not every affidavit needs a notary. Under 28 U.S.C. § 1746, any matter that would normally require a sworn, notarized affidavit in federal proceedings can instead be supported by an unsworn written declaration signed under penalty of perjury.3Office of the Law Revision Counsel. 28 USC 1746 – Unsworn Declarations Under Penalty of Perjury The declaration carries the same weight as a notarized affidavit, and Federal Rule of Civil Procedure 56 treats affidavits and declarations as interchangeable for summary judgment purposes.2Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment
Some states have adopted similar rules; many still require traditional notarization for at least some filings. Check your court’s specific requirements before drafting. If you’re filing in federal court, a declaration under penalty of perjury will almost always be enough. If you’re in state court, assume notarization is required unless you’ve confirmed otherwise.
Signing in Front of the Notary
When notarization is required, do not sign the affidavit ahead of time. A notary who follows the rules will refuse to notarize a pre-signed document because they need to witness your signature themselves. Pre-signing is one of the most common mistakes.
Bring the completed but unsigned affidavit and a valid government-issued photo ID such as a driver’s license or passport. The notary verifies your identity, administers a verbal oath or affirmation asking you to swear or affirm the statements are true, watches you sign, then completes the jurat and applies the official seal.
You can find notaries at banks, law offices, shipping stores, and courthouses. Mobile notaries will travel to you, and most states now allow remote online notarization through a live video call with electronic signing and identity verification. Fees vary by state but typically range from a few dollars to $25 per signature.
Fixing an Error After Signing
For a typo or transposed number, you can sometimes correct the original document by hand. Cross out the incorrect text, write the correction nearby, and have both you and a notary initial the change in the margin. The notary will re-administer the oath, and you’ll sign again below your original signature. This only works for small, non-substantive fixes.
For a substantive error, prepare an entirely new affidavit. It should acknowledge the earlier one, identify the incorrect statements, explain why the error occurred, and provide the corrected information. This supplemental affidavit goes through the same signing and notarization as the original, and both documents become part of the record.
Filing and Serving
Make several copies before filing, and keep at least one for yourself. You’ll need to reference the affidavit throughout the case, and it may come up in depositions or at trial.
Many federal courts and a growing number of state courts use electronic filing through systems like CM/ECF. Before uploading, redact personal identifiers such as full Social Security numbers, dates of birth, and financial account numbers.4United States Courts. Electronic Filing (CM/ECF) If your court doesn’t use e-filing, submit the original notarized affidavit to the clerk in person or by mail. Expect a filing fee either way.
You also have to serve a copy on every other party. Service means delivering the document according to the court’s rules, which specify acceptable methods (personal delivery, mail, or electronic service) and deadlines. Hiring a process server generally costs between $45 and $125 depending on location and speed.
Where an Affidavit Won’t Carry You
An affidavit is strongest in pretrial motions. Its usefulness drops at trial, where a written out-of-court statement is generally inadmissible as hearsay unless it fits a recognized exception. One exception covers situations where the person who wrote the affidavit is unavailable — deceased, seriously ill, refusing to testify despite a court order, or unlocatable through reasonable efforts. Certain prior statements can then come in, though a party can’t deliberately make a witness unavailable and then substitute the affidavit.5Legal Information Institute. Federal Rules of Evidence Rule 804
In criminal cases, the restrictions run tighter. The Sixth Amendment gives every defendant the right to confront the witnesses against them, and prosecutors generally cannot substitute an affidavit for live testimony.6Library of Congress. Amdt6.5.1 Early Confrontation Clause Cases – Constitution Annotated If you’re preparing an affidavit tied to a criminal matter, expect to testify in person if the case goes to trial.
What a False Statement Costs
Everything in a sworn affidavit carries the weight of testimony given in open court. Knowingly including a false statement is perjury, a federal felony punishable by up to five years in prison.7Office of the Law Revision Counsel. 18 USC 1621 – Perjury Generally The statute applies to traditional sworn affidavits and to unsworn declarations made under penalty of perjury alike. State perjury laws add their own penalties, and most treat it as a felony as well.
The credibility damage matters too. If the opposing side catches even one provably false statement, they can use it to impeach everything else you’ve said. If you aren’t certain something is true, leave it out. Five solid facts beat ten with two shaky ones.