How to Write an Affidavit for Illinois Family Court

What is an affidavit?

An affidavit is a sworn written statement of facts that you sign under oath before a notary public. In Illinois family court, affidavits are used to support petitions, motions, and modification requests. Courts treat the contents of a properly executed affidavit as the equivalent of sworn testimony.

Unlike a letter or a narrative, an affidavit carries legal weight precisely because it is signed under penalty of perjury. A false statement in an affidavit can expose you to criminal liability and will damage your credibility in the case. Write only what you know from personal knowledge.

Structure of an Illinois affidavit

An Illinois family court affidavit follows a standard structure:

1. Caption — the name of the court, the case number, and the names of the parties (same as on your petition).
2. Opening paragraph — identifies you: “I, [Full Name], being duly sworn on oath, state as follows:”
3. Numbered factual paragraphs — each paragraph states a single, specific fact in the first person, past tense: “On March 15, 2025, at approximately 3:00 p.m., [Respondent] failed to return the children at the agreed pickup time.”
4. Concluding paragraph — “Further affiant sayeth not.” or “I declare under penalty of perjury that the foregoing is true and correct.”
5. Signature line and notary block — your signature, date, and space for the notary seal and signature.

Notarization is required

An affidavit that is not notarized is not a valid affidavit in Illinois family court. You must sign the affidavit in the physical presence of a notary public. The notary verifies your identity and witnesses your signature.

Where to find a notary in Illinois:

• UPS Store locations (fee typically $5–$10 per signature)
• Banks and credit unions (often free for account holders)
• Circuit Court clerk's office (check availability)
• Libraries in Cook County and many other counties
• Remote online notarization services (check Illinois rules for acceptability)

Do not sign the affidavit before you are in front of the notary — your signature must occur in the notary's presence. Bring a valid, government-issued photo ID.

Common mistakes

Avoid these common affidavit errors that weaken your case or cause the court to discount your submission:

• Vague statements — “He is a bad parent” tells the court nothing. Substitute specific dated incidents: “On January 10, 2025, Respondent did not attend the child's school conference despite written notice.”
• Legal conclusions — “He is in contempt of court” or “She is an unfit parent” are conclusions reserved for the judge. State the facts and let the judge draw conclusions.
• Hearsay without attribution — “I heard he lost his job” is weak. Either state only what you personally know or properly attribute the statement: “On April 2, 2025, Respondent told me he had been terminated.”
• Future predictions — affidavits state past facts, not opinions about what might happen.
• Emotional language — words like “cruel,” “evil,” or “manipulative” are characterizations, not facts. They often backfire by making the affiant look biased.

Using your affidavit effectively

Once your affidavit is notarized, use it as follows:

• Attach it as an exhibit to your petition or motion. Mark it as “Exhibit A” and reference it in the body of your petition.
• Serve a copy on the other party at the same time you serve the petition or motion. Failure to serve is a procedural defect.
• File the original with the circuit court clerk. Keep a copy for your records.
• At hearings, you may be asked to confirm the contents of your affidavit under oath. Make sure every statement in it is accurate — opposing counsel will look for inconsistencies.