How to get clients to pay on time: the path from the signed SOW to the money

When a 12-person agency waits 70 days for an invoice due in 30, the cause is often not the client’s cash but something settled, or left open, before the project began: a clock that starts on “receipt of a proper invoice”, a milestone nobody can show was accepted, a purchase order that was never issued.

Three papers decide it:

• The MSA holds the payment terms for every project: net 30 or net 60, when the clock starts, what happens to a disputed line, interest on late amounts, and whether you may pause the work. The ten clauses to read, payment among them, are in How to review a client’s MSA.
• The SOW holds the schedule of this project: each amount, what triggers it, and how the client accepts a deliverable. Our statement of work template ties each payment to a milestone the client accepts.
• The purchase order, if the client uses them, is the number their AP matches your invoice against. No PO, no match, no payment.

If you get one change into the paper, make it the start of the clock: “within thirty (30) days after the invoice date”, not “after receipt of a properly submitted invoice”. The first is a date both sides can see. The second depends on their mailroom. Net 60 payment terms has the counter-wording, and SOW payment terms has the clause for the SOW itself.

1. 1

   Terms in the paper

   Net days, the start of the clock, interest, a pause right. Before signature.

2. 2

   Vendor setup

   Their supplier form, your tax form, bank details, the PO. The week you sign.

3. 3

   A schedule with dates

   Each amount, its trigger, the date the plan expects it. The day the deal is won.

4. 4

   An invoice AP can pay

   The right entity, the PO, the lines from the SOW. On the trigger.

5. 5

   A reminder before the due date

   A check that it reached AP, then a note a week before.

6. 6

   The overdue letters

   3, 10 and 30 days late, each with a different ask.

7. 7

   The final notice and the call

   The last letter, and the founder on the phone.

8. 8

   A change order for new work

   So the new work has a price and a trigger before it starts.

The rest of this page goes through them. Each step links to the article with the full wording.

A mid-size client does not pay people. It pays suppliers that exist in its payables system, and you become one through a short, dull process that nobody on the buying side will start for you. Start it the day the SOW is signed, by writing to your contact and asking who in AP onboards new suppliers.

What their AP usually asks for:

• A supplier form with your legal name, address, remittance email and the person to contact about payments.
• A tax form. A U.S. client asks for a Form W-9, which gives it your taxpayer identification number for the information returns it files with the IRS.¹ A UK client asks for your company number and VAT number, if you have one.
• Bank details on your letterhead, often with a call-back to confirm them. Welcome the call: it protects you from someone who sends them a “new bank account” in your name.
• A certificate of insurance, if the MSA requires coverage.

What you should ask them for in the same email:

• The purchase order number for this SOW, or confirmation that they do not use POs for services.
• The exact legal entity to bill. A group with five companies pays from one of them.
• The AP inbox or supplier portal where invoices go, and whether an invoice sent to your contact counts as received.
• Their payment run: which days they pay, and how many days an invoice needs to be approved before a run.

An invoice that a payables clerk cannot match goes into a queue, or comes back to your contact, who is on vacation. Before you send, check it against this list.

Send the invoice as a PDF, and put the amount, the due date and the PO in the body of the email too. A clerk who can read the essentials without opening the file routes it faster.

At a small firm, the person who sold the deal is often the one who has to ask for the payment, and it feels like asking a friend to pay back a loan. Two things make it easier.

First, separate the two roles in the letters. Invoices and reminders come from a billing address and a plain voice; the founder steps in at 30 days, as the person who wants the relationship to work. Second, ask for a date, not for money. “Can you tell me which payment run this is in?” is a question a client can answer without losing face. How to ask a client for payment has the words for the email and for the call.

An objection to one line. Ask for the line and the reason in writing, and ask them to pay the rest by the due date. If the invoice is wrong, cancel it and issue a correct one with a new number. Do not edit an invoice that is already in their system: their AP matches by number, and two versions under one number get both held.

New work. A request that is not in the SOW gets a change order before the work starts: what it adds, what it costs, and when that amount is invoiced. Without one, the extra work has no trigger and no invoice, and it turns into a dispute about the last milestone. Our change order template is a one-page Word file.

Interest. Interest on late payment is collectable when the contract names it. The late payment fee clause has the wording for the U.S. and the UK, and what a client usually strikes.

Tommos (tommos.ai) is a CRM whose AI agents, the tommos, take a B2B inquiry to a signed contract. On the Sign plan, Tommo Closer does the steps of this page after the contract: from the signed paper to the reminder.

1. 1

   The scheduleSign

   When a deal is won, Tommo Closer reads the signed SOW or MSA in the client's folder and proposes the payment schedule on a card: each amount, its date or its event, and its payment term. An amount due on an event gets the date the paper's own plan expects, and says where it read it. A person accepts or changes the card. If the paper gives no terms, Tommo asks a person.

2. 2

   The eventSign

   On the expected date of an event, if the record does not show it, Tommo asks the person who runs the work whether it happened.

3. 3

   The invoiceSign

   When an amount is due, Tommo proposes the invoice on a card: the customer, the recipient, the lines, the amount, the due date, the PO number and the letter. “Make the invoice” makes it in your invoice system (Mercury today) and sends nothing. “Send” sends the letter with the PDF and the payment link. No invoice is made or sent without a person’s approval. For work by the hour, the invoice comes from the timesheets your team already sent the client.

4. 4

   The remindersSign

   A paid invoice is read from Mercury, or a person marks it paid. An unpaid one gets a reminder that Tommo writes on a card: by default 3 days after the due date, then every 7 days, 3 in all, and you can change all three numbers. After the last one, Tommo gives the invoice to a person.

5. 5

   The objectionSign

   If the client objects to an invoice, Tommo answers from the record. If the invoice must change, one card cancels it and makes the correct one.

Before the paper is signed, the same plan has Tommo Legal read the client’s MSA against your positions, payment terms included.

How Tommo Closer works · Every plan

• Payment reminder email: three letters before and on the due date, with the PO and the link.
• Overdue invoice email: what to send 3, 10 and 30 days late, and to whom.
• Final notice for an unpaid invoice: what the last letter may say, and when to call instead.
• How to ask a client for payment: the words for the founder who sold the deal.
• Milestone payment schedule: milestones for services work, and an event with no date.
• SOW payment terms: the clause language for the statement of work.
• Late payment fee clause: contract wording for the U.S. and the UK.
• Retainer invoice: retainer, deposit and proforma, and the wording of each.
• Change order template: a one-page Word file for new work on a signed SOW.
• Up: How to review a client’s MSA and the statement of work template.

• The date the money arrives is decided in the MSA and the SOW, before the work starts.
• Get set up in the client’s payables system the week you sign, and ask for the PO and the entity.
• Give every amount a trigger, an expected date and a term.
• Check each invoice against what AP matches: entity, PO, SOW lines, due date as a date.
• Remind before the due date, then 3, 10 and 30 days after, then a final notice.
• Correct a wrong invoice by cancelling it and issuing a new one, never by editing it.

This is not legal advice. It comes from practice; for a large unpaid amount, an hour of a lawyer’s time is worth it.

1. IRS, “About Form W-9, Request for Taxpayer Identification Number and Certification”, read Oct 15, 2026