The customer didn't pay your final invoice. Demand letter, mechanics' lien, or both?
A Washington contractor-side collection has two questions a generic unpaid-invoice analysis does not: was the contractor properly registered with the Department of Labor and Industries when the work was done (because RCW 18.27.080 bars an unregistered contractor from filing suit to collect), and is the 90-day mechanics' lien window under RCW 60.04.091 still open or already closed. Those two facts move the analysis. A registered contractor inside the lien window has the strongest leverage in the state: file the lien, attach the lien to the demand letter, and most owners pay before the foreclosure clock matters. An unregistered contractor outside the lien window has almost no leverage and may not be able to sue at all.
The registration question
Under RCW 18.27.080, a contractor must be properly registered with Washington L&I both at the time the work began and at the time suit is brought to recover compensation for the work. Lapses in coverage during the work window can bar recovery even if the contractor was registered when the contract was signed. Before drafting a demand letter, verify the registration history at the L&I contractor-lookup tool for the entire work period. If there is a gap, the unpaid-invoice strategy changes: the demand letter cannot credibly threaten litigation that the statute bars, and the leverage shifts to commercial negotiation only.
The mechanics' lien window
RCW 60.04.091 sets the lien-recording window at 90 days from the date the contractor ceased to furnish labor, professional services, materials, or equipment. The lien must be recorded in the county where the property is located. The window is strict; recording on day 91 produces an invalid lien that can itself be a CPA claim if asserted. If the work ended 60 days ago, you have 30 days of window left and the lien is the strongest pre-litigation tool. If the work ended 100 days ago, the lien is unavailable and the matter is a generic unpaid-invoice collection.
RCW 60.04.171 then gives an eight-month deadline from the date of recording to file suit to foreclose the lien. A recorded lien that is not timely foreclosed is extinguished. Most matters settle before the eight-month foreclosure clock matters, because the lien clouds title and the owner cannot sell, refinance, or close on financing while the lien is recorded. That is the leverage.
Lien plus demand letter is the standard contractor collection
The standard pre-litigation move on a registered-contractor unpaid invoice is: (1) record the mechanics' lien in the property county before day 90, (2) send the demand letter the same week with a copy of the recorded lien attached, (3) state a 15-business-day window for payment in exchange for lien release. The recorded lien is the document that converts the matter from "we will eventually sue you" into "your title is currently encumbered, here is the release form, here is the payoff." Most homeowners and small commercial owners pay within the window because they have to: lender refinancing, escrow closings, and title insurance all stop while the lien is on record.
What the contractor unpaid-invoice demand letter should do
- State the contractor's L&I registration number and the registration history covering the work period.
- Identify the contract, work performed, and the unpaid invoice with a per-diem statutory interest calculation under RCW 19.52.010.
- Attach the recorded mechanics' lien (if filed) and reference the foreclosure deadline under RCW 60.04.171.
- Reference RCW 4.84.330 if the contract has a fee clause; cite the lien-foreclosure fee provision at RCW 60.04.181 if a lien is recorded.
- Demand payment of a specific number, with payment instructions and an offer to release the lien upon receipt of cleared funds.
- State the next step: lien foreclosure action in superior court if payment is not received by the deadline.
- Send certified mail with return receipt to the owner of record (verified via county assessor records) and to the lender if known.
Watch for the customer's defect-notice posture
If the customer raised a written defect complaint before the demand letter went out, the matter may also implicate Chapter 64.50 RCW (45-day pre-suit notice on residential construction defect claims) from the customer's side. The customer's notice runs against your foreclosure action if a defect counterclaim is asserted. That is a fact-intensive analysis: send the file for the $125 written evaluation before sending a contractor-side demand letter on a defect-disputed project, because the worst outcome is a recorded lien plus a CPA counterclaim if the lien is asserted on a contested file.
Documents to upload before the letter goes out
- The signed contract or written proposal with scope, price, and milestone payment terms.
- Every change order, in writing where possible.
- The invoices (or progress billings) in the form sent.
- Lien-prerequisite notice records: pre-claim notice if one was required (RCW 60.04.031), the notice-to-customer required at contract signing for residential single-family work (RCW 18.27.114).
- Photographs of the work and any completion or punch-list signoff.
- The L&I registration history printout for the work period.
- The county assessor record showing current ownership.
- Any written communications from the customer about quality, defect, or payment.
When this becomes worth hiring an attorney
- Principal at issue above roughly $3,000, with a property that can support a lien.
- Inside the 90-day lien window with verified L&I registration.
- A residential or commercial property with title equity (lien against a property in foreclosure or with no equity is leverage in name only).
- No formal written defect notice from the customer (or the defect notice has already been resolved).
What I review when you send the file
I confirm L&I registration first (because that question can end the analysis), then check the 90-day lien window, then read the contract and invoices. I form a view on whether to record a lien before the demand letter, whether to send a letter without a lien, or whether the case is too defect-disputed to justify either. The output is a written evaluation. If the registration history has a gap or the lien window has closed, I will say so.
Primary sources
- RCW 18.27.080: registration prerequisite to suit.
- RCW 60.04.091: 90-day mechanics' lien recording window.
- RCW 60.04.171: eight-month foreclosure deadline.
- RCW 60.04.181: prevailing-party attorney fees in lien foreclosure.
- RCW 4.84.330: reciprocal fees on contract.
- RCW 19.52.010: 12 percent default interest.
This page is an educational resource. Sergei Tokmakov is a California attorney (CA Bar #279869) currently seeking admission to the Washington State Bar. Nothing on this page creates an attorney-client relationship, and nothing on this page is Washington legal advice for a specific matter.