The difference between an affidavit and a certification comes down to who is in the room when you sign. An affidavit is a written statement sworn before a notary or other authorized official, while a certification is a written statement you sign yourself under penalty of perjury with no third party present. Under federal law, both carry the same legal force in most proceedings.1Office of the Law Revision Counsel. 28 USC 1746 Unsworn Declarations Under Penalty of Perjury Which one you need depends on what the form, rule, or court is asking for.
What Each Document Is
An affidavit is signed by an “affiant” who appears in person before a notary public or other official authorized to administer oaths. The notary verifies the signer’s identity, watches the signing, administers the oath or affirmation, and completes a certificate confirming all of that happened. That third-party step is what makes it an affidavit rather than a letter.
A certification, properly called an unsworn declaration under penalty of perjury, needs no notary. It gets its legal authority from specific statutory language the signer includes in the document itself. Federal law requires this exact wording for declarations signed inside the United States: “I declare (or certify, verify, or state) under penalty of perjury that the foregoing is true and correct. Executed on (date).” For documents signed abroad, the phrase “under the laws of the United States of America” must be added after “under penalty of perjury.”1Office of the Law Revision Counsel. 28 USC 1746 Unsworn Declarations Under Penalty of Perjury Without that clause, a written statement is just a written statement.
You already sign certifications more often than you realize. Federal tax returns, immigration forms, and many court filings use them precisely because Congress decided a notary shouldn’t be required every time someone puts their name to a factual statement for the government.
How They Compare
The practical differences are procedural, but procedure matters when a filing deadline is looming.
- Third-party involvement. An affidavit needs a notary or other authorized official. A certification needs no one but you.
- Cost. Notarization fees vary by state and generally run between $5 and $15 per signature for in-office visits. Mobile notaries who travel to you charge significantly more. A certification costs nothing.
- Convenience. A certification can be signed anywhere, at any time. An affidavit requires scheduling with a notary, presenting valid identification, and appearing in person.
- Legal weight. In federal proceedings, they are equivalent. A signed declaration under penalty of perjury can substitute for a sworn affidavit almost everywhere in federal law.1Office of the Law Revision Counsel. 28 USC 1746 Unsworn Declarations Under Penalty of Perjury
That last point surprises people. The extra ceremony of an affidavit does not give it extra authority. The federal perjury statute treats false statements in both sworn affidavits and unsworn declarations as the same crime with the same maximum penalty.2Office of the Law Revision Counsel. 18 USC 1621 Perjury Generally
When You Need One Specifically
Federal Courts and Agencies
Federal courts treat affidavits and declarations as interchangeable. The Federal Rules of Civil Procedure explicitly allow either one to support or oppose motions, including summary judgment. Both must be based on personal knowledge, set out facts admissible as evidence, and show that the signer is competent to testify on the subject.3Legal Information Institute. Federal Rules of Civil Procedure Rule 56 Summary Judgment
Federal agencies also accept certifications broadly. That is why you sign your tax return under penalty of perjury instead of getting it notarized. The statute authorizing this substitution has only three narrow exceptions: depositions, oaths of office, and oaths that must be taken before a specific official other than a notary public.1Office of the Law Revision Counsel. 28 USC 1746 Unsworn Declarations Under Penalty of Perjury Outside those, a certification works wherever a federal affidavit would.
State Courts
State courts are less uniform. Many states have adopted rules similar to the federal one, letting declarations under penalty of perjury stand in for sworn affidavits in most filings. Others still require notarized affidavits for specific proceedings, particularly in probate matters, real estate transactions, and certain family law filings. Before you file in state court, check the local rules. This is the one area where the choice between the two documents genuinely matters, and getting it wrong can mean a rejected filing.
Read the Form’s Language
The wording on the form is usually the clearest signal. If it says “affidavit,” start with a notarized affidavit. Some courts will accept a declaration in its place, but that is not a gamble worth taking on a deadline. If it says “declaration,” “certification,” or “under penalty of perjury,” no notary is needed.
The Penalty for Lying Is the Same Either Way
Lying in either document is a federal crime. The federal perjury statute covers both scenarios in separate subsections, and the maximum penalty for either is five years in federal prison, a fine, or both.2Office of the Law Revision Counsel. 18 USC 1621 Perjury Generally
A separate federal statute covers false statements made to government agencies, which often arrive through certifications on official forms. A materially false statement to any branch of the federal government carries up to five years in prison, and up to eight years if it relates to certain serious offenses like terrorism or sex trafficking.4Office of the Law Revision Counsel. 18 USC 1001 Statements or Entries Generally Whether you swore an oath in front of a notary or signed a penalty-of-perjury clause at your kitchen table, the consequences for a material lie are identical.
Remote Online Notarization
The traditional friction of an affidavit has always been physically getting to a notary. Remote online notarization, which lets a signer appear before a notary over a live video connection rather than in the same room, has changed that. Most states now authorize some form of remote notarization, a trend that accelerated during the pandemic. The notary still verifies identity and administers the oath; the process just happens through audio-visual technology.
Remote notarization does not eliminate the formality gap between affidavits and certifications, but it does shrink the convenience gap. If you need a notarized affidavit and cannot easily visit a notary in person, check with your state’s secretary of state for current rules, because the requirements for identity verification and approved platforms vary.
Choosing When You Have a Choice
When the instructions specify one document or the other, follow them. When they do not, a certification is usually the simpler option. It costs nothing, takes minutes, and carries the same legal weight in federal proceedings.
The scenarios where an affidavit adds value beyond what the law strictly requires are narrow. One is a business transaction where the other side’s attorney specifically asks for a notarized statement. Another is when the document may need to be used internationally and authenticated through an apostille or embassy legalization process, both of which start from a notarized signature. Outside situations like those, the certification does the same work with none of the errands.