Construction late payment interest is money you are legally entitled to charge when a general contractor or owner pays you past the due date — and in most states, prompt payment statutes set a mandatory interest rate that applies even if your contract is silent on the subject. Depending on the state, that statutory rate runs from 1% per month (Florida, under Fla. Stat. § 255.073 and § 715.12) to 2% per month (California, under Cal. Bus. & Prof. Code § 7108.6 on public works) to a flat 18% per year in some jurisdictions. The rate applies to subcontractors, sub-subcontractors, and material suppliers. Failing to put a late payment clause in your contract does not eliminate your rights — but it may limit you to the statutory rate rather than a negotiated one.
What Is the Statutory Interest Rate for Late Payments in Construction?
Every state with a prompt payment law sets a default interest rate that kicks in when payment is overdue, whether your contract mentions interest or not. The rates vary, but here are the figures for key states:
- Florida: 1% per month (12% per year) on payments not made within the timeframes in Fla. Stat. § 715.12 (private work) and Fla. Stat. § 255.073 (public work). Interest begins accruing on the day after the payment due date.
- California: On public works contracts, interest accrues at 2% per month under Cal. Pub. Cont. Code § 7107(f) when retention is wrongfully withheld. On private projects, the prompt payment penalty under Cal. Civ. Code § 8800 includes 2% per month on amounts wrongfully withheld.
- Texas: Under Tex. Gov't Code § 2251.025 (public) and Tex. Prop. Code § 28.004 (private), interest accrues at 1.5% per month on overdue payments.
- Arizona: Under Ariz. Rev. Stat. § 32-1129.02, interest on private project late payments runs at 1% per month.
- Washington: Under RCW 39.76.011, interest on late public works payments accrues at 1% per month.
- Nevada: Under NRS 624.628, interest on late payments to subcontractors runs at 1.5% per month on public projects.
- Oregon: Under ORS 701.630, interest on late residential and commercial construction payments accrues at the legal rate of 9% per year (0.75% per month) for private projects.
If your contract specifies a higher rate, the contract rate governs in most states — but it cannot be unconscionable or violate state usury laws.
Does a Subcontractor Contract Require a Late Payment Interest Clause?
No — a contract clause is not required to charge late payment interest in states with prompt payment statutes. Statutory interest applies automatically when payment is overdue, regardless of whether the contract addresses it. That said, silence in your contract can hurt you in two ways.
First, without a contract clause, you are capped at the statutory rate. If the statute sets 1% per month and you negotiate 1.5% in your subcontract, you collect 1.5% — a clause gives you leverage. Second, some states require the GC to notify you in writing of any disputed amount within a specific window (for example, Texas requires notice within 14 days of receipt of an invoice under Tex. Prop. Code § 28.003). Without a matching clause in your subcontract, you may not know the clock is running.
The practical fix: put a late payment clause in every subcontract that (1) names the interest rate, (2) sets the due date, and (3) makes the GC responsible for your attorney fees if you have to collect. More on attorney fees below.
How Much Interest Can a Subcontractor Charge on a Late Payment?
The amount you can charge depends on three things: the statutory rate in your state, any rate in your contract, and whether you are on a public or private project. Using the rates above, here is what late payment interest looks like in real numbers on a $50,000 invoice that goes 90 days past due:
- At 1% per month (Florida, Arizona, Washington): $50,000 × 1% × 3 months = $1,500
- At 1.5% per month (Texas, Nevada): $50,000 × 1.5% × 3 months = $2,250
- At 2% per month (California public works): $50,000 × 2% × 3 months = $3,000
Those numbers grow fast. A $100,000 invoice sitting unpaid for six months at 1.5% per month accumulates $9,000 in interest before you ever file a claim. According to Rabbet's 2024 Construction Payments Report, 82% of contractors face payment waits of over 30 days — meaning the majority of subcontractors have a legal right to interest charges they are never collecting.
How to Calculate Interest on an Unpaid Construction Invoice
Calculating interest on an unpaid construction invoice is straightforward once you have three numbers: the principal (the unpaid invoice amount), the monthly rate, and the number of months (or days) past due.
Simple interest formula: Interest = Principal × Monthly Rate × Number of Months
Step-by-step example:
- Invoice amount: $35,000
- State: Texas (1.5% per month under Tex. Prop. Code § 28.004)
- Payment due: 30 days after invoice submission
- Invoice submitted: March 1; payment due: March 31
- Actual payment received: June 30 (90 days late = 3 months)
- Interest: $35,000 × 0.015 × 3 = $1,575
For partial months, convert to a daily rate. Divide the monthly rate by 30 to get a per-day rate, then multiply by the exact number of days late.
Daily rate example (Texas):
- Daily rate: 1.5% ÷ 30 = 0.05% per day
- 45 days late on a $35,000 invoice: $35,000 × 0.0005 × 45 = $787.50
Document every calculation in writing and attach it to your demand letter. Courts and arbitrators expect to see the math.
Can You Charge Compound Interest on an Overdue Construction Payment?
In most states, prompt payment statutes authorize simple interest only — not compound interest. Compound interest (where you charge interest on the accumulated interest) is generally not allowed under state usury laws unless the contract explicitly authorizes it and the rate does not exceed the state's legal maximum.
Florida, Texas, California, and most other states with prompt payment acts specify simple interest in the statute language. If compound interest is not expressly permitted by the statute or your contract, a court is unlikely to award it. The safer and more enforceable approach: calculate simple interest accurately, add attorney fees where permitted, and let the total demand do the work.
What Are the Prompt Payment Law Penalties for a General Contractor?
Beyond interest, most state prompt payment statutes impose additional penalties on GCs who fail to pay on time without a legitimate reason for withholding. These penalties exist to deter bad-faith delay, and they can significantly increase the total amount you recover.
Common statutory penalties include:
- Florida: Under Fla. Stat. § 715.12(3), if a GC fails to pay within the required period and cannot demonstrate a valid dispute, the subcontractor may recover the full amount due plus interest, plus attorney fees and court costs.
- Texas: Under Tex. Prop. Code § 28.005, a GC who wrongfully withholds payment is liable for the unpaid amount plus 18% per year interest (separate from the monthly prompt payment rate), plus attorney fees.
- California: Under Cal. Pub. Cont. Code § 7107(f), wrongfully withheld retention on public works triggers a 2% per month penalty on top of the retention amount, plus attorney fees.
- Washington: Under RCW 39.76.011, a GC who fails to pay interest when due is liable for the interest plus attorney fees and court costs.
The key phrase in most statutes is "without reasonable cause." A GC who withholds payment because of a genuine, documented dispute is generally protected. A GC who withholds because cash flow is tight is not.
Can You Collect Attorney Fees Along With Late Payment Interest?
Yes — in most states, prompt payment statutes explicitly allow subcontractors to recover reasonable attorney fees when they successfully collect overdue payments. This is a significant protection because it removes the "it costs too much to sue" argument a GC might count on.
States where attorney fees are explicitly available to subcontractors in prompt payment disputes include Florida (Fla. Stat. § 715.12), Texas (Tex. Prop. Code § 28.005), California (Cal. Pub. Cont. Code § 7107 on public works), Washington (RCW 39.76.011), and Arizona (Ariz. Rev. Stat. § 32-1129.02).
To maximize your chances of recovering fees: (1) send a written demand before filing suit that cites the applicable statute and states the total interest accrued, (2) document all collection costs including time spent, and (3) include an attorney fees clause in your subcontract for private work where statutory coverage may be narrower.
Attorney fees clauses are one-way in most states — meaning if the contract says the prevailing party gets fees, you benefit if you win. Make sure your contract has one.
How Do Lien Rights Connect to Late Payment Interest?
Late payment interest and mechanics lien rights are separate remedies, but they work together. Interest compensates you for the time value of money during the delay. A mechanics lien secures the underlying debt against the property. Filing a lien — or preserving your right to file one by serving a preliminary notice — is often what motivates a GC to pay in the first place.
According to Rabbet's 2024 Construction Payments Report, slow payments cost the U.S. construction industry an estimated $280 billion in 2024, adding roughly 14% to total construction spending. That number exists largely because subcontractors do not consistently use the legal tools available to them: preliminary notices, lien rights, and prompt payment interest claims.
The combination of a filed (or threatened) mechanics lien plus a written demand for accrued interest under the applicable prompt payment statute is your most powerful collection position. A GC who ignores an invoice rarely ignores a lien on the property.
Most states require a preliminary notice to be served early — often within 20 days of first furnishing labor or materials — to preserve lien rights. If you miss that window, you lose leverage.
If you work in Florida, serving a Notice to Owner (NTO) is the mandatory first step to preserving lien rights on private projects under Fla. Stat. § 713.06. Pair it with a prompt payment demand for interest and you have two separate legal hooks working simultaneously.
Frequently Asked Questions
Does the GC have to tell me in writing why they're withholding payment?
In most states with prompt payment statutes, yes. Texas requires the GC to notify you of the reason for withholding within 14 days of receiving your invoice (Tex. Prop. Code § 28.003). Florida requires the GC to serve a written notice specifying the disputed amount before withholding payment past the due date. If the GC withholds without proper written notice, they lose the protection of the dispute exception and interest begins accruing automatically.
What if my contract says payment is "when paid" or "if paid"?
Pay-when-paid clauses make the owner's payment to the GC a condition of when you get paid — not whether you get paid. Most courts, including those in Florida, Texas, and California, treat these clauses as timing provisions, not as eliminating your right to payment entirely. Pay-if-paid clauses (which attempt to shift the risk of owner nonpayment to you) are enforceable in some states but void in others, including California and New York. Prompt payment interest rights may still apply even under a valid pay-when-paid clause once a reasonable time has passed.
Do I have to put the interest rate in my invoice, or can I add it later?
You can add a separate interest demand later. Best practice is to reference the applicable statute in your original demand letter and calculate interest from the first day of default. Courts do not require the original invoice to mention interest — they care about the statutory right and your calculation showing the days overdue.
Is there a minimum dollar amount before I can claim prompt payment interest?
No. State prompt payment statutes do not set a minimum invoice amount for interest to accrue. A $2,000 invoice that goes 60 days past due generates the same statutory right to interest as a $200,000 invoice. The practical question is whether it is worth the effort to pursue — which is why a strong contract clause and a pre-suit demand letter matter.
Can I charge interest if I don't have a written subcontract?
Yes, in most cases. Prompt payment statutes protect subcontractors based on the project relationship, not the form of the contract. Oral subcontracts are generally enforceable in construction, and statutory interest rights attach to the payment obligation itself. The harder problem is proving the original amount owed, which is why written contracts (even simple ones) protect you.
What happens if the GC pays the principal but ignores the interest demand?
You can still pursue the unpaid interest as a separate claim. In most states, you can file a mechanics lien for the accrued interest in addition to the principal — interest that has accrued before the lien is filed can be included in the lien amount in Florida, Texas, and several other states. Alternatively, you can pursue it in small claims court or through arbitration, depending on your contract terms.
Can a GC deduct backcharges to avoid paying interest?
A GC can assert legitimate backcharges to reduce the amount owed. However, the disputed portion must be clearly identified in writing within the statutory window. Prompt payment statutes typically require the GC to pay the undisputed portion of an invoice on time — withholding the full invoice because of a partial backcharge dispute exposes the GC to interest on the undisputed balance. Document your dispute responses in writing immediately.
Does prompt payment interest apply on retainage?
Yes. Most state prompt payment statutes explicitly cover retainage as well as progress payments. Florida's prompt payment act (Ffl. Stat. § 715.12) includes retainage in its definitions. California's Cal. Pub. Cont. Code § 7107 specifically addresses wrongfully withheld retention with a 2% per month penalty. If your retainage sits past the due date after substantial completion, interest is accruing.
Protect Your Lien Rights Today
Late payment interest is money you have already earned — the statute just makes it official. But interest demands work best when the GC knows you are also holding a loaded lien right. If you have not served a preliminary notice on your current jobs, you may already be losing leverage without knowing it.
Use the LienFlash deadline calculator to see exactly how much time you have left to file on each active project. For most states, the window is tight — and missing it means you are collecting on goodwill alone.
LienFlash generates attorney-reviewed preliminary notices in about 2 minutes, sends them via USPS Certified Mail, and gives you a Certificate of Mailing PDF to prove service. One notice costs $24.99. The lien right it preserves can be worth multiples of your entire contract value in negotiating power.