I assumed that the factual allegation in a complaint were always assumed true so an affidavit by the Plaintiff verifying the accuracy of the factual allegation would appear unnecessary, or? Why is this done?


There are several reasons to verify a complaint (i.e. to swear that its factual allegation are true).

1. This is required for certain kinds of claims in certain jurisdictions as a matter of statute or court rule, which vary widely.

For example, in Colorado, a "replevin claim" (i.e. a claim for expedited recovery of possession of specific tangible personal property) must be verified, and the object will be repossessed by force under court order if a timely response is not filed, often in a matter of a week or two, when the lack of a response could be due to reasons other than a lack of a good defense to the seizure.

Generally speaking, this is required when the relief requested is extraordinary relative to an ordinary lawsuit to collect an unpaid bill or recover damages from an injury in an accident, but requirements vary considerably from one jurisdiction to another.

Historically, at least, there have been jurisdictions in which all complaints must be verified, and there are other jurisdictions where it is almost never required.

2. The lawyer wants to insulate himself from liability.

A lawyer is required to exercise due diligence to confirm that the facts in documents filed with a court are true. Normally, a lawyer is entitled to simply rely on the fact that this lawyer's clients are telling the truth. But, if the client is sketchy, it is hard to independently confirm the facts, or the facts alleged seem extraordinary, the lawyer can be mostly insulated from liability for sanction for filing a complaint that lacks a factual basis by having a client swear to the fact under penalty of perjury.

3. A motion for summary judgment is likely.

In most U.S. jurisdictions, if a party defending a claim provides a factually detailed affidavit in support of a motion to dismiss a case because the facts alleged in the complaint are not true, the claim against that party will be dismissed unless the party bringing the claim files a response to the motion for summary judgment supported by a factually detailed affidavit disputing the facts alleged in the defending party's affidavit on material issues that creates a "disputed issue of fact" that must be resolved in an evidentiary hearing or trial by a judge or jury.

If the initial complaint contains factually detailed assertions in support of its allegations that are verified, i.e. sworn it as if by an affidavit, then that route to ending the case prematurely with a motion for summary judgment is largely thwarted. This can be a particularly valuable tactic for a plaintiff is the plaintiff may not be someone whom it is easy for the plaintiff's lawyer to contact on short notice.


Generally, things in a complaint will be questioned or you would not be going to court. There are different circumstances where an affidavit is used so I can't list every instance here, but most of the time when a complaint is filed, at least part of it is not already on the record and would therefore be like testimony being entered, where you are sworn before testifying.

My state, Illinois, even has laws regarding it. In Illinois when they cite that law or attach a separate affidavit, they are acknowledging they complied with that law. http://www.ilga.gov/legislation/ilcs/documents/073500050K1-109.htm

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    The statute linked goes to how it is done, rather than when it must be done, permitting an unnotarized declaration under penalty of perjury rather than a notarized verification or affidavit.
    – ohwilleke
    Oct 24 '19 at 22:22
  • The statute includes affidavits, "bill of particulars, answer to interrogatories, affidavit,". As I said in the answer, it would be used when the complaint alleges something that is not solely a matter of law, is of record all already, or must be verified to be true for some other reason.
    – Putvi
    Oct 24 '19 at 22:34
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    @Putvi This is not what the Illinois statute that you cite means. Unverified complaints and answers alleging factual matters can be and routinely are filed in Illinois. It is simply saying that anything that would have had to have been sworn before a notary prior to the enactment of the statue can instead be signed under penalty of perjury without a notarization.
    – ohwilleke
    Oct 28 '19 at 17:33
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    @Putvi Even if Illinois law does have such a requirement, this statute doesn't create it. It says "Unless otherwise expressly provided by rule of the Supreme Court, whenever in this Code any . . . document or pleading filed in any court of this State is required or permitted to be verified, or made, sworn to or verified under oath, such requirement or permission is hereby defined to include a certification of such pleading, affidavit or other document under penalty of perjury as provided in this Section." This statute doesn't define what documents are required or permitted to be verified.
    – ohwilleke
    Oct 28 '19 at 18:13
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    The main relevant IL statute is: "(735 ILCS 5/2-605) (from Ch. 110, par. 2-605): "Verification of pleadings. (a) Any pleading, although not required to be sworn to, may be verified by the oath of the party filing it or of any other person or persons having knowledge of the facts pleaded. . . . . If any pleading is so verified, every subsequent pleading must also be verified, unless verification is excused by the court. . . ." It is optional in an initial complaint or if excused by the court. People verify is for procedural advantage, not because it is required in a complaint alleging facts.
    – ohwilleke
    Oct 28 '19 at 18:17

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