Illinois asks subcontractors for two different mailings, both by certified mail with return receipt requested, both served the moment they are placed in the mail. One is early and residential; the other comes at the end of the job.
The 60-day notice to an owner-occupant (60/21(c))
"Each subcontractor who has furnished, or is furnishing, labor, services, material, fixtures, apparatus or machinery, or forms or form work for an existing owner-occupied single family residence" notifies the occupant or the occupant's agent "within 60 days from the subcontractor's first furnishing" (60/21(c)). It states the subcontractor's name and address, the date work or deliveries started, the type of work done and to be done, and the name of the contractor requesting the work; it warns the owner to obtain lien waivers before paying; and it carries the NOTICE TO OWNER warning in at least 10-point bold type.
"Any notice given after 60 days by the subcontractor shall preserve the subcontractor's lien, but only to the extent that the owner has not been prejudiced by payments made prior to receipt of the notice." Service is personal or by "certified mail, return receipt requested"; "notice by certified mail is considered served at the time of its mailing."
The notice of claim (60/24)
Subcontractors and parties furnishing labor, materials, fixtures, apparatus, machinery or services under the contractor give "the owner of record or the owner of record's agent or architect, or the superintendent having charge of the building or improvement" — and "the lending agency, if known" — written notice of the claim and the amount due or to become due. It "may at any time after making his or her contract with the contractor, and shall within 90 days after the completion thereof" be given, or within 90 days after final delivery of extra or additional work or material (60/24(a)).
Section 24 supplies a permissive form ("To (name of owner): You are hereby notified that I have been employed by … to … under his or her contract with you, on your property at … and that there was due to me, or is to become due … the sum of $…"). "Notice shall be considered served at the time the written notice is placed with the delivery service or in the mail." Once served, the owner retains funds under 60/27.
The return receipt is part of the method
Both sections name "certified mail, return receipt requested" (60/24(a) also allows a nationally recognized delivery service and personal delivery). Because the receipt is part of the enumerated method, these two notices are mailed with the USPS electronic return receipt as standard, not as an add-on.