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How do you check a plumbing license in Illinois?

The Illinois Department of Public Health licenses plumbers, plumbing contractors and apprentice plumbers under the state's plumbing license law. Its plumbing page links a plumbing license lookup and says plumbing ads must include the plumbing license number, which gives you a number to search.

Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

The license lookup is yours to run on the state's site.

InstaBids is an AI-run marketplace for homeowners and property managers: describe a home job once, by chat or through your own AI assistant, add photos, and get multiple written quotes on the same scope, compared apples to apples, with no phone calls or home visits before you pick.

By InstaBids editorial team with AI research agents. Sources last read: 22 October 2026

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Key facts

Where do you find an Illinois plumber's license number?

Start with the plumber's own advertising. The department's plumbing page, read 22 October 2026, lists a plumbing license lookup in its Resources list, so open the lookup from that page, listed in the sources below, and search the number you were given.

Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

The Illinois General Assembly's site, read 22 October 2026, carries the full text of that law. On advertising, its section 5(b) reads: "No person who provides plumbing services may advertise those services unless that person includes in the advertisement the license number that is required to be displayed under subsection (a)."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

On work vans and trucks, section 5(a) adds: "The number of the license so displayed shall also be included with the plumbing identification on vehicles."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

The department's page also gives a renewal date: "Plumber licenses must be renewed by April 30th following the date of issuance via the online renewal page."

Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

When is a plumber also a plumbing contractor in Illinois?

The department's plumbing page puts it this way: "Plumbing Contractors are any licensed plumber or apprentice plumber who performs work for another person."

Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

The definitions in section 2 of the law read: “"Plumbing contractor" means any person who performs plumbing, as defined in this Act, for another person.”

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

Registration runs on a yearly cycle. Section 13.1 of the law, on plumbing contractor registration, reads: "All plumbing contractor registrations expire on the last day of September of each year."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

What insurance and bond papers does a plumbing contractor file?

Two kinds of paper go to the department with a registration. On insurance, section 13.1(4) reads: "Applicants shall submit an original certificate of insurance documenting that the contractor carries general liability insurance with a minimum of $100,000 per occurrence, a minimum of $300,000 aggregate for bodily injury, property damage insurance with a minimum of $50,000 or a minimum of $300,000 combined single limit, and workers compensation insurance with a minimum $500,000 employer's liability."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

The same subsection continues: "Certificates must be in force at all times for registration to remain valid."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

On the bond, section 13.1(5) reads: "Applicants shall submit, on a form provided by the Department, an indemnification bond in the amount of $20,000 or a letter of credit in the same amount for work performed in accordance with this Act and the rules promulgated under this Act."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

The definitions name the agency behind those forms: “"Department" means the Illinois Department of Public Health.”

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

Which plumbing work falls outside the license law?

Small fixes and sewer lines. The definition of plumbing in section 2 ends with a list of exclusions, among them: "nor does it mean or include minor repairs which do not require changes in the piping to or from plumbing fixtures or involve the removal, replacement, installation or re-installation of any pipe or plumbing fixtures."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

The same definition closes: "Plumbing does not include the installation, repair, maintenance, alteration or extension of building sewers."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

Apprentices are part of the trade too. The department's page describes the path to a full license: "To obtain a license, individuals must pass a state licensing exam after working under a licensed plumber as a licensed apprentice for a 48 to 72 month period."

Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

On supervision, section 3(4)(a) reads: "A licensed apprentice plumber shall plan, design and install plumbing only under the supervision of the sponsor or his or her agent who is also an Illinois licensed plumber."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

Section 3(4)(e) caps the number: "No licensed plumber may, in any capacity, supervise more than 2 licensed apprentice plumbers at the same time."

Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

What should you ask before an Illinois plumber starts work?

Ask for the numbers in writing first, then run the department's lookup yourself as an optional public-record step. These steps are practical suggestions, not department rules.

  1. Ask for the plumber's license number, and compare it with the number on the ad or the van.
  2. If a business does the job, ask whether its plumbing contractor registration is current; registrations run out on the last day of September each year.

    Source: Illinois General Assembly, Plumbing License Law (225 ILCS 320), read 22 October 2026.

  3. Before you sign, ask the business for a copy of its certificate of insurance.
  4. Ask who will work on site, and whether an apprentice will work under a sponsor or agent on your job.
  5. Open the plumbing license lookup from the department's plumbing page and search the number you were given.

    Source: Illinois Department of Public Health, plumbing page, read 22 October 2026.

  6. Note the date you searched and what the lookup showed, and keep it with your contract.

Who sees your contact details when you post a job on InstaBids?

One point about InstaBids follows. Contact details stay hidden until the homeowner picks a contractor and they confirm the connection.

Source: InstaBids process and privacy, live-page excerpts, read 22 October 2026.

Post your job on InstaBids, and contractors can bid in writing on one written scope.

Homeowners anywhere in the US can post a job; once you send it, InstaBids finds contractors to bid on it.

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