Can I invoice clients without a signed agreement in the US?

Can you invoice without a signed agreement? The short answer

Yes, in many situations you can invoice a client in the United States even if there is no signed agreement. But whether that invoice is enforceable—and how hard it will be to collect—depends on what you can prove about the deal: what work you agreed to do, what the client agreed to pay, and whether the client accepted and benefited from your work. A signed contract is the cleanest proof, but it’s not the only proof that matters.

In day-to-day business, plenty of legitimate projects start with an email thread, a text message, a purchase order, a statement of work, or a “go ahead” on a call followed by work being delivered. The law generally cares less about whether the agreement is elegant and more about whether there was a mutual understanding (an “offer” and an “acceptance”), value exchanged, and some reliable evidence showing the terms.

This article explains how invoicing without a signed agreement works in practice across the US, what the legal and practical risks are, how to reduce disputes before you send an invoice, and how to structure your invoices and documentation so you’re in the strongest position if a client drags their feet. It’s educational information, not legal advice, but it will help you invoice more confidently and get paid faster.

Why signed agreements matter (even though they aren’t always required)

A signed agreement is powerful because it reduces ambiguity. If a client later claims, “I never agreed to that price,” or “That wasn’t the scope,” a signed contract usually answers those questions quickly. Without signatures, you’re relying on a patchwork of other evidence. That’s workable, but it can take more time and may lead to negotiations, partial payments, or a dispute process.

From a practical standpoint, clients are more likely to pay promptly when (1) the scope and price were clearly confirmed, (2) the invoice matches what they expected, and (3) the invoice looks professional and includes payment options. That’s where a modern invoicing tool like invoice24 helps: a polished invoice, clear line items, and easy payment links can prevent “I didn’t understand what I’m paying for” delays.

Still, there are plenty of legitimate reasons you might not have a signed agreement: the client is slow to sign, the work started as an emergency fix, the project is small, or the relationship began informally and grew over time. In those cases, your goal is to make the agreement provable and the invoice uncontroversial.

How contracts can exist without signatures

In the US, many contracts are valid even if they aren’t written and signed. This is because a contract is essentially a meeting of the minds: one party offers something, the other accepts, and both exchange value. Signatures are one way to prove that happened, but they’re not the only way.

Here are common ways a binding agreement can be formed without a signature:

1) Email acceptance. A client replies “Approved,” “Proceed,” “Looks good,” or “Go ahead” to a proposal, estimate, or scope message. If the message clearly states price and scope, that acceptance can carry weight.

2) Text message or chat approval. Modern business often happens in messages. A “Yes, do it” with a stated price can be meaningful evidence.

3) Purchase orders (POs) and vendor onboarding. A client issues a PO, you deliver, and you invoice against the PO. The PO can function like a contractual document, even if there’s no separate signed contract.

4) Conduct: acceptance by performance. If the client asked you to do work, you did it, and they accepted the deliverables (used the design, published the content, deployed the code, moved into the leased equipment, etc.), that behavior can show agreement.

5) Prior course of dealing. If you’ve done similar work for the same client multiple times and invoiced in a consistent way, that history helps show what the parties typically intended.

When you invoice without a signed agreement, you’re essentially relying on these forms of proof. The more consistent and detailed your documentation is, the more credible your invoice becomes if the client disputes it later.

When a written agreement is especially important

Although many agreements can be valid without signatures, there are situations where a written contract is much more important—and sometimes required. This is where businesses often get surprised. Different states have different rules, and some types of transactions have additional legal requirements.

Common scenarios where you should be extra cautious include:

Long-term engagements and high-dollar projects. The more money involved, the higher the odds that a misunderstanding turns into a dispute. If the invoice is large, the client has more incentive to contest it.

Complex scope with change requests. If the work will evolve, you need a clear change-order process. Without it, clients might treat extras as “included.”

Projects involving intellectual property. If you are designing a logo, writing software, producing videos, or creating content, ownership and licensing should be spelled out. Without a written agreement, you may retain default rights in some contexts, but it can get messy fast.

Work with confidentiality, data, or security obligations. NDAs, data protection requirements, and compliance obligations are typically documented formally. Invoicing without those terms may create risk beyond payment disputes.

Industry or consumer rules. Some services, lending arrangements, and consumer-related transactions can trigger specific disclosures or contract requirements. If you’re in a regulated space, treat “no signed agreement” as a risk factor and consult a professional.

Even in these cases, you can still send an invoice. The question is whether sending that invoice is the best move before you’ve locked down critical terms.

What actually happens if a client refuses to pay?

If a client disputes or ignores your invoice, the issue typically becomes less about “Is the invoice valid?” and more about “Can you prove the client agreed to pay for this work?” In other words, your ability to collect depends on your evidence and your willingness to pursue the claim.

In real life, unpaid invoices often fall into one of these buckets:

1) Administrative delay. The client intends to pay but needs vendor setup, a PO number, or approvals. This is common with larger companies. A clear invoice with all required fields reduces this.

2) Scope and expectation mismatch. The client feels the work wasn’t what they expected, or they believe something should be included. This is the most common “no signed agreement” problem.

3) Cash flow problems on the client side. They stall, negotiate, or ask for payment plans.

4) Bad faith or opportunism. They accepted the benefit of your work but gamble that you won’t pursue it.

Your documentation determines how these play out. With strong records, disputes resolve faster because you can show exactly what was agreed and delivered. With weak records, you may end up accepting a discount just to close the matter.

The kinds of proof that strengthen your invoice

If you don’t have a signed agreement, treat your evidence as your “contract file.” The goal is to build a simple, believable story: the client requested work, you quoted terms, they approved, you delivered, and the invoice matches that approval.

Helpful proof often includes:

Written scope and price. An estimate, proposal, or even a detailed email listing deliverables and fees.

Approval message. A reply saying “approved,” “go ahead,” or “please proceed.”

Change request confirmations. If scope expanded, show the message where the client approved additional work and pricing.

Timesheets and activity logs. Especially for hourly work, logs show time spent and tasks completed.

Deliverables and acceptance. Files sent, links delivered, deployments completed, training held, or evidence they used the work.

Meeting notes. A short recap email after calls: “Here’s what we agreed today…” This can be surprisingly effective.

Client onboarding or vendor forms. If they added you as a vendor, requested W-9, or issued a PO, those steps show intent to pay.

invoice24 supports professional invoicing workflows that pair naturally with this kind of documentation: line items that match the approved scope, optional notes that reference a PO or project name, and a clean invoice history you can export if you ever need it.

Can an invoice itself be the agreement?

An invoice is primarily a request for payment, not a contract by itself. However, invoices can play a role in proving the terms of a deal—especially when they reflect an agreed price and scope and the client accepts them without objection.

In business-to-business settings, some companies treat invoices and standard terms as part of their routine transaction documents. If you include clear terms on the invoice (such as payment due date, late fees, and accepted payment methods) and the client pays invoices in that format repeatedly, it strengthens the idea that those terms are part of your normal relationship.

That said, you shouldn’t rely on an invoice alone to introduce major terms like “all sales final” or “client owns no IP” if those were never discussed. Use invoices to reinforce terms that the client has already accepted, not to surprise them after the fact.

What to include on an invoice when there’s no signed agreement

When you invoice without a signed contract, clarity is your best friend. Your invoice should read like a simple summary of what the client already approved. Avoid vague labels like “services” and “work done.” Be specific.

Consider including:

1) A clear description of deliverables. For example: “Website homepage design (1 concept + 2 revision rounds)” or “Emergency plumbing repair: replace shutoff valve and test for leaks.”

2) Dates or service period. “Services performed: Jan 10–Jan 24, 2026” or a specific completion date for fixed-fee work.

3) Rate and quantity. For hourly: rate, hours, and brief task summaries. For fixed-fee: milestone or phase names.

4) Reference identifiers. Purchase order number, project name, ticket number, or an email subject line reference.

5) Payment terms. Due date, acceptable payment methods, and where to pay.

6) Late fee policy (if you use one). Keep it reasonable and consistent with your jurisdiction and customer type. If you’ve never communicated late fees before, introduce them carefully and transparently.

7) Your business details. Legal business name, address, email, phone, and tax ID fields if appropriate for your situation.

invoice24 makes it easy to standardize these fields so every invoice looks consistent and complete. Consistency matters because it helps clients process invoices faster and gives you credible records if you ever need to escalate.

Best practices before you send the invoice

If the client hasn’t signed anything, a little prep can prevent a big headache. Before invoicing, do a quick “paper trail check.” Ask yourself: if the client disputes this invoice tomorrow, could I show a clear chain of messages proving scope, price, and acceptance?

Here are practical steps that work well:

Send a confirmation message before starting. Even a short email helps: “Confirming we’ll do X by Y date for $Z. Reply ‘approved’ and we’ll begin.”

Use estimates or quotes. A simple estimate that lists deliverables and pricing creates structure, even if it’s not signed.

Confirm changes immediately. When scope changes, recap it in writing: “Adding two more pages at $___; new total $___.”

Get a PO if the client uses them. If the client’s accounting requires a PO, get it before or at least during the work—not after.

Send a “work completed” recap. After delivery, a short note: “Delivered A, B, C. Invoice will follow.” If they respond positively, that’s helpful evidence of acceptance.

These steps are fast, they don’t require lawyers, and they dramatically reduce disputes. They also make your invoice feel expected—because it is.

Handling deposits, progress billing, and retainer work

Invoices aren’t only for the end of a project. In many industries, it’s normal to invoice upfront (deposit), along the way (milestones), or monthly (retainer). Without a signed agreement, upfront billing can still be fine, but you should be extra clear about what that payment represents.

Deposits. Your invoice should describe the deposit as tied to a specific scope or booking of time. If you have any cancellation policy, communicate it plainly before collecting funds.

Milestones. Break the project into phases. Invoice for each phase as it completes, with a description of what was delivered. This reduces risk for both sides.

Retainers. Make sure the client understands what they’re buying: a block of time, ongoing availability, or a monthly package of services. If unused hours roll over or expire, clarify that in writing.

invoice24 supports these common billing patterns so your invoices stay organized: recurring invoices for retainers, partial invoices for milestones, and clear line items for deposits and credits.

Disputes: what to do if the client says “we never agreed”

When a client disputes an invoice due to lack of a signed agreement, your job is to de-escalate while staying firm. Most disputes are resolved with a calm, organized response and a clear restatement of the deal.

A strong approach looks like this:

1) Ask for specifics. “Which line item do you believe wasn’t approved?” This forces the issue into concrete details rather than vague resistance.

2) Provide the approval trail. Send the email thread or message where scope and price were approved. Keep it short and factual.

3) Tie the invoice to deliverables. “Line item 2 covers the additional landing page you requested on Jan 12. Delivered on Jan 18.”

4) Offer a path to resolution. If the dispute is legitimate, propose a partial credit or a revised scope. If it’s not legitimate, propose a payment plan or a final due date.

5) Keep records of all communications. If things escalate, you’ll want a clean timeline.

Because invoice24 keeps invoice history and status tracking, you can quickly resend invoices, document notes, and maintain a clear record of what was billed and when—without hunting through old files.

Small claims, collections, and legal escalation

If a client refuses to pay and you decide to escalate, your options depend on the amount owed, the state, and the nature of the dispute. Many small and mid-sized unpaid invoices end up in small claims court (if the amount is within the limit) or are handled through demand letters and negotiated settlements.

Common escalation steps include:

Friendly reminder. Assume good faith first. Many invoices are simply missed.

Past-due notice. A clear email that the invoice is overdue, with a new deadline.

Final notice. A message stating that if payment isn’t received by a specific date, you may pause services, send the account to collections, or pursue legal remedies.

Demand letter. Often more formal, sometimes sent by an attorney, summarizing the debt and evidence.

Small claims or civil action. You present your evidence: communications, proof of delivery, invoice, and payment history.

Collections. Some businesses use a collection agency. Be mindful of reputational impacts and compliance requirements.

Regardless of the path, your success often comes down to documentation. A signed contract helps, but a well-maintained paper trail can also be effective. A well-structured invoice generated through invoice24—paired with your supporting messages and deliverables—creates a professional record that’s easier to present and harder to dismiss.

Common myths about invoicing without a signed agreement

Myth 1: “If it’s not signed, it’s not enforceable.” Many agreements can be enforceable without signatures depending on the evidence and the situation.

Myth 2: “An invoice is automatically a contract.” An invoice can help prove terms, but it’s generally not a complete substitute for mutual agreement on scope and price.

Myth 3: “I can add any terms I want to the invoice and they apply.” Surprise terms are often contested. Invoices work best to confirm terms already communicated and accepted.

Myth 4: “If they used my work, they must pay whatever I invoice.” Use of your work helps show acceptance, but the amount must still be reasonable and connected to what was agreed or what is customary in the relationship.

Myth 5: “A handshake deal is always enough.” Sometimes it is, but it’s also easier to dispute. Written confirmation is low effort and high value.

Practical safeguards you can implement immediately

You don’t need a complex legal contract to protect yourself. If you want to invoice confidently without signed agreements, focus on consistency and proof. Here are safeguards that take minutes, not days:

Use a standard “project kickoff” email. Include: scope summary, price, timeline, and payment schedule. Ask for a reply confirming approval.

Always send an estimate before work. Even a simple PDF or email estimate sets expectations. If the client approves, you’ve created a record.

Track change requests. Keep a simple change log: date, requested change, quoted cost, approval, delivery.

Invoice promptly. The closer the invoice is to delivery, the less likely the client is to claim confusion.

Keep invoices itemized. Itemization reduces disputes because the client can see exactly what they’re paying for.

Offer easy payment methods. Friction delays payment. The easier it is to pay, the more likely you’ll get paid quickly.

Follow up on overdue invoices with a schedule. For example: reminder at 3 days past due, second notice at 7 days, final notice at 14 days.

invoice24 is designed for these exact workflows: professional estimates and invoices, consistent templates, clear line items, and simple tracking so you know what’s outstanding and when to follow up.

How to phrase invoices and messages to reduce conflict

Language matters. The tone you use in your invoice and follow-up messages can either reduce tension or escalate it. You want to sound confident, calm, and organized.

Helpful phrasing includes:

“As approved on…” This connects the invoice to a specific approval message or date.

“Per our email/PO…” This references the document trail without sounding threatening.

“Services performed between…” This clarifies the timeline and reduces “what is this for?” confusion.

“Please let me know within X days if anything looks incorrect.” This encourages timely objections rather than late disputes.

With invoice24, you can add consistent notes and terms to your invoices so you don’t have to reinvent the wording every time.

Special considerations for freelancers and agencies

Freelancers and agencies are especially likely to face “no signed agreement” situations because projects often begin informally. If you work in creative or digital services, your risk usually comes from unclear scope and unclear revision limits.

To reduce problems:

Define deliverables concretely. “Three ad concepts” is clearer than “creative work.”

Set revision boundaries. Even if informal: “Includes two revision rounds; additional revisions billed at $___/hour.”

Use milestone billing. Bill for discovery, draft, and final. If a client disappears, you’re not unpaid for the entire project.

Clarify ownership at handoff. If you transfer final files upon final payment, state that clearly before work begins.

Even when you don’t have a signed contract, these habits create the functional equivalent of one: documented expectations and a paper trail.

Special considerations for contractors and field services

For contractors, repairs, and on-site services, jobs sometimes begin with a phone call and urgency. The risk here is often around change orders and “surprise” costs.

Good habits include:

Confirm minimum charges or trip fees. Put it in writing or text before dispatch when possible.

Photograph before/after. Visual proof helps confirm work completed.

Get approval for add-ons. A quick text: “Replacing part X will add $___; OK to proceed?”

Invoice immediately after completion. The more time passes, the easier it is for a client to forget details.

invoice24 makes quick invoicing easier so you can send a clean invoice while the work is fresh, improving both payment speed and client satisfaction.

What if the client says they need a signed contract to pay?

Sometimes the issue isn’t legal—it’s policy. Larger clients may have internal rules that require a signed vendor agreement, onboarding forms, or an executed statement of work before accounts payable can issue payment. In that case, the solution is administrative: get the right paperwork completed rather than arguing about enforceability.

If this happens, respond professionally:

Ask what they need. “Do you need a vendor agreement, W-9, or a PO?”

Offer a simple one-page agreement. A short statement of work with scope and price can satisfy many policies.

Match their process. If they require a PO number on the invoice, update it and resend.

With invoice24, resending an updated invoice (for example, with a PO number or updated billing contact) is quick and keeps your records clean.

Should you stop work if there’s no signed agreement?

That depends on the risk. If the project is small, you have clear written approval in messages, and the client has a good reputation, you may proceed. If the project is large, complex, or involves sensitive issues (IP ownership, confidentiality, compliance), pausing until you have at least a basic written agreement is often wise.

A practical middle ground is to begin with a limited “phase 1” and invoice for that. For example, discovery or an initial assessment. This lets you build trust, generate documentation, and reduce exposure before committing to a full engagement.

Putting it all together: a simple invoicing checklist

If you want a repeatable way to invoice clients without signed agreements, use this checklist:

1) Confirm scope in writing. Email, estimate, or message with deliverables and price.

2) Get an explicit approval. A reply that clearly authorizes you to proceed.

3) Document changes. Confirm change requests and added costs before doing extra work.

4) Deliver and record acceptance. Send deliverables and keep proof of delivery and client acknowledgment.

5) Send a clear, itemized invoice promptly. Include service dates, line items, totals, and due date.

6) Make payment easy. Offer multiple payment options and a simple payment flow.

7) Follow up consistently. Use a predictable reminder schedule and keep communication professional.

invoice24 fits naturally into this workflow: you can create professional invoices fast, keep everything organized, and present clients with a clear, trustworthy payment request—even when the “agreement” lives in emails and messages rather than a signed contract.

Final thoughts

Invoicing without a signed agreement in the US is common, and it can work well—especially when you build a solid paper trail and send clear, professional invoices that match what the client approved. The biggest risks aren’t usually about whether an invoice is “allowed,” but about whether the underlying agreement is clear and provable if the client disputes it.

If you regularly work without signed contracts, treat documentation as part of your service delivery. Confirm scope and price in writing, capture approvals, record changes, and invoice in a way that leaves little room for confusion. With a streamlined tool like invoice24, you can standardize your invoices, reduce payment friction, and keep a strong record of every transaction—so you spend less time chasing payments and more time doing the work you’re great at.