The best answer to when to send an invoice is almost always the same: send it the day you finish the work or hand over the goods. That default shifts in three situations. Long projects should be billed in stages against defined milestones. Custom work should start with a deposit invoice before any labor begins. Ongoing services should run on a fixed recurring cycle. The timing you pick affects when the payment clock starts, when the IRS expects you to report the income, and how strong your position is if the client refuses to pay.
Send It the Day the Work Is Done
For most one-off projects and product deliveries, the invoice should go out the same day the job wraps up or the goods change hands. The details are fresh, the client just received value, and no one is confused about what was delivered. Under the Uniform Commercial Code, a buyer who accepts goods is obligated to pay the contract price.1Legal Information Institute (LII) / Cornell Law School. UCC 2-607 Effect of Acceptance Notice of Breach Burden of Establishing Breach That obligation attaches at acceptance, so the invoice should arrive while acceptance is still obvious to both sides.
Prompt invoicing also engages a doctrine called account stated. When a client receives an invoice showing a balance and doesn’t dispute it within a reasonable time, courts in many states treat that silence as agreement that the debt is valid.2Cornell Law Institute. Account Stated The longer you wait to bill, the easier it becomes for a client to argue the charges are wrong or the work was incomplete. A same-day invoice locks in the terms while both parties remember what happened.
Speed matters for one more reason. Every state sets a deadline after which you can no longer sue to collect an unpaid debt. For written contracts, that window typically runs from three to ten years depending on the state, and the clock generally starts when payment was due, not when you got around to billing.3Consumer Financial Protection Bureau. Can Debt Collectors Collect a Debt Thats Several Years Old Invoicing immediately fixes a clear due date and preserves the full collection window.
Send a Deposit Invoice Before Work Begins
For custom work, the first invoice should go out before any labor starts. A deposit invoice, issued right after the client signs the contract, confirms their financial commitment and helps cover initial costs like materials and subcontractors. If the client won’t pay the deposit, you learn that before you’ve invested time.
Common deposits run 25% to 50% of the total project cost. For hourly professionals, a retainer serves the same function as a prepaid balance drawn down as work is performed. Attorneys are the familiar example: bar rules in every state require lawyers to hold unearned client funds in a dedicated trust account, separate from the firm’s operating account, until the work is actually completed.
Make the start of work explicitly contingent on receiving the deposit, and put that language in the contract itself, not just the invoice. If the client stalls on paying, you have a written basis for holding off without breaching the agreement.
Send Invoices at Milestones on Long Projects
Large or long-running engagements shouldn’t wait for a single invoice at the end. Progress billing ties payment requests to specific deliverables throughout the project, so you aren’t financing months of labor out of pocket. A construction firm might invoice after site preparation, again after framing, and once more at final inspection. The contract should spell out which milestones trigger an invoice and what documentation the client needs to approve payment.
Payment terms like Net 30 or Net 15 start running when the client approves the milestone deliverable, not when you submit the invoice. That distinction matters. If a client takes two weeks to review your work and another 30 days to pay, you’re looking at six weeks between finishing a phase and seeing the money. Build that delay into your cash flow planning and keep milestone deliverables clearly defined so the approval step doesn’t drag out.
Retainage on Construction Contracts
On construction projects and some other large contracts, the client withholds a percentage of each progress payment until the whole project is done. This holdback, called retainage, typically runs 5% to 10% of each invoice. Federal procurement rules cap retainage at 10% of the approved amount and require agencies to release the full amount promptly once all contract requirements are satisfied.4Acquisition.gov. Progress Payments Under Construction Contracts If your contract includes retainage, each milestone invoice should separate the amount due now from the amount being held back, and you should track the retained total so there are no surprises at closeout.
Bill on a Fixed Cycle for Recurring Services
Ongoing services like consulting, software access, or monthly maintenance call for a fixed billing cycle instead of project-based invoicing. Most businesses bill on the first or fifteenth of the month to align with standard corporate accounting periods. The main decision is whether to bill in advance for the upcoming period or in arrears for work already performed.
Billing in advance is better for cash flow and reduces collection risk because the client pays before receiving the service. If they stop paying, you stop the service. Billing in arrears makes more sense when the scope varies month to month, since you can’t know the total until the period ends. Either way, the service agreement should state the billing date, payment terms, and what happens if payment is late.
Consistency matters more than the specific date. Once you set a billing cycle, stick to it. Clients budget around predictable invoices, and irregular billing creates friction that delays payment for no good reason.
Timing and Late Fees
Late fees only work if the client agreed to them before the invoice went past due. The contract or service agreement should state the fee clearly, including the percentage or flat amount and when it applies. Most businesses charge 1% to 2% per month on the unpaid balance, or a flat fee in the $25 to $50 range.
Every state sets limits on the interest rate you can charge, and those limits vary widely. Some states have no statutory cap for commercial transactions; others restrict rates to as low as 5% annually. Charging above your state’s limit can void the entire interest charge and, in some jurisdictions, expose you to penalties. Keep the rate modest and clearly documented in the signed agreement.
Federal contractors work under a different rule. Under the Prompt Payment Act, federal agencies that pay late owe interest automatically at a rate set by the Treasury Department, which is 4.125% for the first half of 2026.5U.S. Department of the Treasury. Prompt Payment That interest accrues from the day after payment was due through the date the agency actually pays, and the agency must pay it without you having to ask.6Office of the Law Revision Counsel. 31 USC 3902 Interest Penalties If you invoice a federal agency, prompt billing directly determines when that clock starts.
How Invoice Timing Affects Your Taxes
When you send an invoice can shift when you owe taxes on the income, and the rules depend on whether you use the cash method or the accrual method of accounting.
Cash Method
Most sole proprietors and small businesses use the cash method, which means income is reported in the year the payment is actually received.7Internal Revenue Service. Publication 538 – Accounting Periods and Methods If you finish a project in December 2026 but the client pays in January 2027, that income falls on your 2027 return. Watch the constructive receipt rule, though. If payment was available to you before year-end but you deliberately avoided collecting it to push income into the next year, the IRS can treat it as received in the earlier year.8eCFR. 26 CFR 1.451-2 Constructive Receipt of Income A client mailing a check on December 28 that arrives January 3 is fine. Telling a client to hold off on an already-prepared payment until January is not.
Accrual Method
Under accrual accounting, income is reported when it’s earned, regardless of when the client pays. The trigger is the “all events test”: once all events have occurred that fix your right to receive the income and you can determine the amount, the income is taxable.7Internal Revenue Service. Publication 538 – Accounting Periods and Methods For most invoice-based businesses, that means income is recognized when the goods are delivered or the service is completed, not when the check arrives. Invoicing promptly after completion keeps your books aligned with when the IRS expects the income to be reported.
Corporations and partnerships generally must use the accrual method unless their average annual gross receipts over the prior three tax years were $32 million or less, which qualifies them for the cash method.9Internal Revenue Service. Rev Proc 2025-32 Qualified personal service corporations in fields like law, consulting, and health care can use the cash method regardless of revenue.
Prove the Invoice Was Delivered
The timing you chose only matters if you can prove the client got the invoice. Email is the standard delivery method, and accounting platforms like QuickBooks or FreshBooks add read receipts and payment tracking that plain email can’t match. An electronic invoice arrives instantly, and many platforms let the client pay directly with a single click.
Whatever method you use, keep proof of delivery. An email with a read receipt, a delivery confirmation from an invoicing platform, or certified mail with a return receipt all work. A timestamp and delivery confirmation are far more persuasive in court than “I’m pretty sure I sent it.” That documentation is especially important for the account stated doctrine, where the client’s failure to dispute the invoice within a reasonable time can be treated as acceptance of the debt.2Cornell Law Institute. Account Stated