What Does “Under Penalty of Perjury” Mean? Penalties and Uses

When you sign a document under penalty of perjury, you are making a legally binding promise that everything in it is true, and that promise carries the same weight as testimony given under oath in a courtroom. A knowing, material lie on that document is a federal felony punishable by up to five years in prison and a fine of up to $250,000.¹²

How the Signed Declaration Replaces an Oath

Federal law lets you sign most documents that would otherwise require a notary or a sworn oath by instead using a written declaration under penalty of perjury. The authorizing statute, 28 U.S.C. § 1746, prescribes the exact language. If you sign inside the United States, the declaration reads: “I declare under penalty of perjury that the foregoing is true and correct.” If you sign abroad, you add “under the laws of the United States of America.”³

Your signature on that line is what triggers the criminal consequences. No judge, no notary, no raised hand. The written declaration does the same work as a courtroom oath, and the law treats a lie on it the same way.

What Actually Counts as Perjury

Not every error on a signed form is a crime. To convict someone of perjury under federal law, prosecutors have to prove three things beyond a reasonable doubt:¹

The statement was made under oath or under a penalty-of-perjury declaration.
The person knew it was false when they made it. An honest mistake or faulty memory does not qualify.
The falsehood was “material,” meaning it had the potential to influence the outcome of the proceeding or the decision being made.

Materiality is the filter that keeps minor errors out of federal court. Lying about your income on a loan application is material because it affects what the lender decides. Writing the wrong middle initial on the same form is not. Prosecutors do not bring perjury cases over details that could not have changed anything.

Where You’ll See the Phrase

Most Americans run into “under penalty of perjury” first on their federal tax return. Every IRS Form 1040 includes the declaration: “Under penalties of perjury, I declare that I have examined this return and accompanying schedules and statements, and to the best of my knowledge and belief, they are true, correct, and complete.”⁴ A return filed without a valid perjury statement can be treated as a legal nullity by the IRS, as if you never filed at all.⁵

Immigration applications are the other big one. When you file a benefit request with U.S. Citizenship and Immigration Services, your signature certifies under penalty of perjury that the application and all supporting evidence are true and correct.⁶ The stakes here are especially steep. Knowingly filing a false asylum application, for example, can mean permanent ineligibility for any immigration benefits and up to ten years in prison under a separate immigration fraud statute.⁷

You’ll also see the phrase on affidavits and declarations submitted as evidence in court, financial disclosures in bankruptcy, applications for government benefits, and many business license forms. In each setting the declaration stands in for an oath and carries the same consequences.

What the Penalties Look Like

Perjury is a federal felony. Under 18 U.S.C. § 1621, conviction brings up to five years in prison, a fine of up to $250,000, or both.¹² That five-year ceiling applies across the federal perjury landscape: court testimony, government forms, and penalty-of-perjury declarations alike.

Criminal exposure is not the only consequence. In civil cases, a judge who finds that a party lied under oath can dismiss that party’s claims or enter judgment against them as a sanction, and a witness caught lying can have their entire testimony thrown out. Those in-case consequences sometimes hurt more than the fine.

How Long Prosecutors Have

Federal prosecutors have five years from the date of the false statement to bring perjury charges, under the general federal statute of limitations for non-capital offenses in 18 U.S.C. § 3282.⁸ The clock starts when the statement is made, not when it’s discovered. A lie buried in a tax return or a court filing can become unprosecutable if no one catches it within that window.

Fixing a False Statement

If you realize you said something false under oath during a federal court or grand jury proceeding, the law gives you a narrow way out. Under 18 U.S.C. § 1623(d), recanting the statement bars prosecution, but only if two conditions still hold when you come clean: the false statement must not have substantially affected the proceeding, and it must not yet be clear that your lie has been or is about to be exposed.⁹

The correction has to happen in the same continuous proceeding, and it has to be unambiguous. Asking to “clarify” or “supplement” earlier testimony is not enough; you have to flatly admit the earlier statement was false.¹⁰ Once a grand jury has already acted on the false testimony or investigators have independently found the truth, no recantation will save you.

This safe harbor applies only to proceedings covered by § 1623, meaning federal court and grand jury testimony. There is no equivalent defense under the general perjury statute, § 1621, which covers documents like tax returns and benefit applications. If you filed a false tax return under penalty of perjury, you can file an amended return, but the amendment does not automatically shield you from prosecution.

Perjury Compared to Lying to the Government

Perjury is sometimes confused with the broader crime of making false statements to the federal government. They are separate offenses under different statutes, and the difference matters because you do not have to be under oath to be charged with making false statements.

The false statements statute, 18 U.S.C. § 1001, makes it a crime to knowingly lie to any branch of the federal government, including in a casual interview with a federal agent or on a form that carries no perjury declaration at all. The maximum penalty is also five years in prison, but § 1001 includes a terrorism enhancement that raises the ceiling to eight years when the false statement relates to domestic or international terrorism.¹¹ The general perjury statute has no comparable enhancement.

The practical dividing line is context. Perjury requires an oath or penalty-of-perjury declaration; § 1001 does not. Section 1001 applies broadly to dealings with federal agencies but specifically excludes statements by parties and their lawyers during court proceedings, which is where the perjury statutes take over. Federal investigators often reach for § 1001 because it is easier to prove: they only need to show the lie was knowing, willful, and material, without having to establish that the speaker was under oath.

Talking Someone Else Into Lying

Perjury law also reaches the person who persuades someone else to lie under oath. That crime, subornation of perjury, is codified at 18 U.S.C. § 1622 and carries the same maximum penalty as perjury itself: up to five years in prison and a fine of up to $250,000.¹²²

If you induce another person to commit perjury, you are guilty of subornation whether or not you said anything false yourself. An attorney who coaches a client to lie on the stand and a business partner who pressures a colleague to sign a false affidavit both face the same felony exposure as the person who actually lied. Subornation charges often travel alongside obstruction of justice charges.

Can You Sue Someone for Lying Under Oath?

Generally, no. American courts have long followed a common law rule that bars civil lawsuits based on another person’s perjury. The reasoning is that allowing perjury-based lawsuits would chill witness testimony and let losing parties endlessly reopen old cases by alleging the other side lied.

If you believe a judgment was based on perjured testimony, the remedy is to ask the court that issued it to vacate the judgment, not to file a separate lawsuit against the witness. The legal system treats the finality of judgments as more important than giving every perjury victim a new cause of action, and leaves punishment of the lie to the criminal justice system.

1
Office of the Law Revision Counsel. 18 USC 1621 – Perjury Generally
2
Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine
3
Office of the Law Revision Counsel. 28 USC 1746 – Unsworn Declarations Under Penalty of Perjury
4
Internal Revenue Service. Form 1040 – US Individual Income Tax Return
5
Internal Revenue Service. Significant Service Center Advice SCA 1998-054
6
U.S. Citizenship and Immigration Services. Chapter 2 – Signatures
7
USCIS. Form I-589, Instructions for Application for Asylum and for Withholding of Removal
8
Office of the Law Revision Counsel. 18 USC 3282 – Offenses Not Capital
9
Office of the Law Revision Counsel. 18 USC 1623 – False Declarations Before Grand Jury or Court
10
United States Department of Justice Archives. Comparison of Perjury Statutes – 18 USC 1621 and 1623
11
Office of the Law Revision Counsel. 18 USC 1001 – Statements or Entries Generally
12
Office of the Law Revision Counsel. 18 USC 1622 – Subornation of Perjury