Overdue Invoice: What to Send on Day 1, Day 7, Day 11 and Day 30

Before any of it works: three fields

The follow-up is only strong if the paperwork underneath it is specific. In the contract I use, the payment section says this, with the brackets being the parts a seller has to fill in:

Late payments accrue [1.5]% per month. Provider may pause
work on invoices more than [10] days overdue after written
notice.

And on the invoice itself, one line under the total:

Late payments: Invoices unpaid after [NET] days accrue
[X]%/month late fee.

Three things have to be numbers before you send anything: the deposit (I use 50% before work begins), the net terms (15 days is my default; "net 30" is a month of free financing you did not agree to give), and the late-fee percentage. If those three are filled in, every message below is just a reminder of something already agreed. If they are blank, the first message turns into a negotiation you are not prepared for.

Day 1: the reminder, assume good faith

The due date passed yesterday. Most of the time this is the whole fix, so the first message is short, friendly, and re-attaches the invoice so nobody has to search for it.

Subject: Invoice #[n] - [Project], due [date]

Hi [Name],

Quick note that invoice #[n] for [amount] was due [date] and
hasn't come through yet. I've re-attached it here in case it
got buried.

Payment details are on the invoice ([method]). If it's already
in process, ignore me and thank you.

[Your name]

Do not apologize for asking, do not explain what you did, and do not add a deadline. There is nothing to escalate yet - you are confirming a fact.

Day 7: the accrual notice, with the arithmetic

A week late is when the tone changes from reminder to record. This message does one new thing: it states the number the contract already promised, in dollars, so the cost of waiting stops being abstract.

Subject: Invoice #[n] - now 7 days overdue

Hi [Name],

Following up on invoice #[n] for [amount], due [date] and now
7 days outstanding.

Under section [x] of our agreement, late payments accrue
[1.5]% per month, so on [amount] that's about $[amount x 0.015]
for a full month past due. I'd rather not add it - let me know
if this is being processed this week and I'll leave it at the
invoice total.

Happy to re-send payment details or split the invoice if
that's the blocker.

[Your name]

The math, on the defaults: 1.5% per month on a $2,000 invoice is $30. That is not a punishment rate - it is a low, ordinary one rather than a penalty, and a client or a court may still read it differently, which is exactly why the number has to be written down before there is a dispute. The "offer to split the invoice" line matters more than it looks: a client who cannot pay the whole thing is the client most likely to pay nothing, and a partial payment is still a payment. To see the same arithmetic run over a longer tail, the late-fee calculator does it offline from the rate you type in - which is the number to bring to a client who says a fee is unreasonable.

Day 11: the written pause notice

This is the message the contract was built for. My clause says work may pause on invoices more than 10 days overdue, after written notice - which means the notice has to exist in writing before the pause is legitimate, and this email is that notice. It is not a threat, it is a schedule change.

Subject: Work paused on [Project] pending payment

Hi [Name],

Invoice #[n] is now 11 days overdue. Per section [x] of our
agreement, I'm giving written notice that I'm pausing work on
[Project] as of today.

Nothing here is personal and nothing is cancelled - as soon as
payment lands, work resumes the same day, and the milestone
dates in Exhibit A shift by the number of paused days (section
[y], client-dependent delays extend deadlines day-for-day).

If there's a problem with the invoice itself, tell me what it
is and I'll fix it today.

[Your name]

Three details do the work. It states the date, so the pause is a fact rather than a mood. It says resumes the same day, so the client's incentive is to pay rather than argue. And it names the day-for-day extension, so the record shows why the dates moved.

Then actually stop. Pausing work while quietly continuing is the one move that makes every future notice in this sequence worthless.

Day 30: final notice, and get a date in writing

A month overdue is no longer a payment problem, it is a relationship decision. This message asks for one thing: a date, in writing. It also states what happens if there is no answer, without pretending you can do more than paperwork.

Subject: Final notice - invoice #[n], [amount], 30 days overdue

Hi [Name],

Invoice #[n] for [amount] is 30 days overdue. Work has been
paused since [date] under section [x].

I'd like to resolve this without involving anyone else. Please
reply with either:
  1. a payment date within the next 7 days, or
  2. the reason you're withholding payment, so I can address it.

If I don't hear by [date], I'll treat this as a termination
under section [z] ([14] days' written notice), invoice for all work
performed to date plus any non-cancellable expenses, and hand the
file to [small-claims / collections].

Either answer is fine. Silence is the only outcome I can't
work with.

[Your name]

The cancellation fee only applies if they end it - if you terminate for non-payment you invoice for work done, not the fee. Get that distinction right in the message or the whole thing reads as a bluff, which it is not supposed to be.

What this sequence cannot do

• It cannot recover from a missing deposit. If you started work without money down, the leverage was gone before the invoice was. That clause is the whole reason the deposit exists.
• It cannot handle a dispute. If the client says the work is wrong, the payment conversation stops and the acceptance/scope conversation starts - that is guide 01's job, and it is why the scope clause has to list what is out of scope.
• It cannot force payment. After day 30 the real options are a small-claims filing (costs and rules vary by state, and this is not legal advice) or writing it off. Both are outside this kit, and the amounts involved decide which one is rational.