Professional liability insurance—sometimes called malpractice insurance or errors and omissions insurance—is insurance that may be purchased by attorneys and law firms to pay the costs of defending legal malpractice claims, and the costs of settling such claims or paying the judgment awarded to a plaintiff on such a claim. Most states do not require attorneys to purchase professional liability insurance, but some states require attorneys who do not carry professional liability insurance to provide notice to their clients of that fact. Some states require attorneys to have their clients sign a written disclosure that the attorney does not have professional liability insurance.

In Illinois, attorneys are not mandated by state law to carry professional liability insurance, also known as malpractice insurance or errors and omissions insurance. However, the Illinois Rules of Professional Conduct require attorneys who do not maintain professional liability insurance to inform their clients of this lack of coverage. Specifically, Rule 1.4 of the Illinois Rules of Professional Conduct mandates that a lawyer who does not have professional liability insurance must communicate this fact in writing to a client at the time of the client's engagement of the lawyer, if the lawyer knows that the lawyer does not have professional liability insurance of at least $100,000 per occurrence and $300,000 in the aggregate. This disclosure must be made to existing clients as well if the insurance coverage later lapses or is no longer maintained. The rule aims to ensure that clients are aware of the potential risks involved in hiring an attorney without malpractice insurance and can make informed decisions about their legal representation.