ZAMBO.

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Finished months ago. Never invoiced. Bill it today.

It sits in the back of your mind at odd hours: a job you finished, delivered, maybe even saw the client use, and the invoice that never got sent. Now months have passed and sending it feels awkward enough that another month goes by. Here is the plain news: finished, delivered, accepted work does not stop being billable because its invoice is late, and the awkwardness is yours, not the client's accounts department's. What a late invoice needs is not an apology essay. It needs the job rebuilt from its record, so the invoice arrives as a fact with dates on it, not as a memory asking to be believed.

See the instrument first: the live demo runs one real call and hands you its verifiable receipt, no signup.

Updated October 26, 2026. The two delivery records quoted below are real and public, with their client decision states read back from the live service on publication day.

Step 1. Accept the real answer first: yes, send it, and send it now

Time limits on chasing a debt do exist in most places, and they are usually measured in years, not months, but they vary and they are not what this page can decide for you. What is true in ordinary business life is simpler: clients pay late invoices from suppliers every week, accounts departments expect them, and the main cost of lateness is the explanation getting longer in your head while the amount stays exactly the same. Every week you wait makes the send feel stranger and the client's records colder. Today is the cheapest day this invoice will ever have. Send it today, with the steps below done in an hour, not perfected for another month.

Step 2. Rebuild the job from its record, not from your memory

Before writing the invoice, assemble the job as it actually happened: the agreement and its price, the delivery date, what exactly was delivered, any acceptance or sign-off, and any later message showing the client using or approving the work. Dates are the whole game here, because the client's first honest question will be whether this job is real, finished, and already counted somewhere in their own books. A reconstruction from messages, files, and the delivery record answers it completely. A reconstruction from memory, however confident, invites the one argument you cannot afford: two people remembering a months-old job differently, with the money going to whoever sounds less sure.

Step 3. Read the two states a finished job can be in

The record format is AER-1, published as an IETF Internet-Draft (draft-zambo-aer1-26), and each step carries a verifiable receipt: a receipt proves the saved result was not changed since it was saved. The two public records below show the states your rebuilt job should be matched against:

Accepted: the decision is on the record

Pending: checked, and still waiting on a decision

An accepted record, 4 of 4 steps checked, decided_by client, release_hint ok_to_release, is the strongest late invoice there is: the client already decided this work was done, on 2026-10-16T14:31:51.146Z in that example, and your invoice is simply the bill arriving after a decision their side already made. A pending record, 5 of 5 steps checked and release_hint hold, means the work was delivered and checked but never formally accepted, so your late invoice should carry the delivery record and ask for the decision and the payment together, in that order, in one message.

Step 4. Send it with one short, honest cover note

The note is three sentences and no more: this invoice is for the named job, delivered on this date and accepted on this date, and it is reaching them late because it was never sent at the time, which was your oversight. Then the amount and the payment details. Do not over-apologize, do not discount unprompted out of embarrassment, and do not dress the delay up as their error. One honest sentence about the lateness does something useful: it removes the mystery. An unexplained invoice from months ago makes a client suspicious; the same invoice with the oversight named reads as a supplier cleaning up their books, which is a completely ordinary thing to receive.

Step 5. Answer the three replies a late invoice usually gets

First reply: we never received an invoice. True, and now answered: here it is, with the job's dates and record attached. Second reply: our contact has left, or the budget for that period is closed. Send the same packet to whoever owns supplier payments now; a closed internal period is their accounting problem to reopen, and documented delivered work is exactly what reopenings are made of. Third reply, the rare honest dispute: we do not think we owe this. Now the packet does its work, agreement, delivery, acceptance, use, and the conversation is about those documents rather than about why the invoice is late. If the amount is large and the refusal is flat, that packet is also what you hand a local adviser in a first meeting, instead of a story.

Step 6. Make the invoice part of delivery, so this cannot recur

The fix is procedural, not motivational: the invoice goes out when the work is accepted, as a step of the delivery itself, never as a separate chore for a quieter week that does not exist. Add a monthly sweep with teeth: one hour, same day each month, where every finished job is checked for its three closing facts, delivered, accepted, invoiced, and any job missing the third gets its invoice that day regardless of age. Shame is a terrible accounting system. A checklist with a date on it has no feelings about your oversight at all, which is precisely why it catches what shame only broods over.

What a record does not settle

A verifiable receipt proves the saved result was not changed since it was saved; it does not set the deadline for billing where you work, does not revive a claim that has genuinely expired, and cannot make a client reopen a closed budget. The agreement, the delivery and acceptance dates, and the record of the work are what a late invoice stands on. This page is general information, not legal advice.

Frequently asked questions

I forgot to send an invoice for work I finished months ago. Can I still bill the client?

Yes, in the ordinary course of business you bill it now. Work that was agreed, delivered, and accepted does not become free because its invoice is late, and clients' accounts departments process late supplier invoices routinely. Rebuild the job from its record before you send: the agreement and price, the delivery date, what was delivered, and any acceptance or sign-off. Date the invoice today, put the delivery and acceptance dates on it, attach that packet, and add one honest sentence in the cover note saying the invoice was never sent at the time and the oversight was yours. Formal time limits for chasing payment do exist and vary by place, usually measured in years rather than months, so for a very old or very large amount, a short check with a local adviser is worthwhile. This page is general information, not legal advice.

How late is too late to send an invoice?

Practically, an invoice gets harder long before it gets impossible. Within the same season, it is a non-event. Across a year end, expect the client to need the delivery record and possibly a fresh supplier form, because their books for the old period are closed and reopening needs documents, which your packet provides. After several years, formal limitation periods may genuinely apply, and those are set by the law where the work was contracted, not by custom. The pattern to notice is that evidence, not courtesy, decides every stage: the older the job, the more the delivery and acceptance record matters and the less your memory does. Send it at whatever age it is, with the record attached, and let documents have the argument.

Should I offer a discount because the invoice is so late?

No, not unprompted. A discount for your own lateness teaches the client that slow paperwork is priced in your disfavor, and it quietly accuses the delivered work of being worth less than the agreed price, which it is not. If the client is a good one and the relationship matters, the goodwill gesture that actually lands is the honest sentence and the clean packet, not money off. The exception is when a discount buys something real in return, such as immediate payment of a genuinely contested old balance in full settlement, stated in writing. That is a negotiation, not an apology, and it should be named as one.

What if the client says they already paid, or never agreed to the work?

Ask for their payment reference, and check it against the job before replying further: occasionally they are right, and an old paid invoice in a different system is exactly the kind of thing a months-later reconstruction can miss, which is why you rebuild from records rather than memory in the first place. If no payment exists, the packet answers the agreement question: the brief or order, the delivery, and the acceptance or the client's visible use of the finished work. Keep every reply attached to those documents and dated. A late-invoice dispute is won by the side whose paperwork is calm, complete, and older than the argument.

How do I make invoicing happen at delivery instead of months later?

Close every job as a handover the client accepts, and invoice off that acceptance the same day, while the decision, the decider, and the date are fresh on the record. When the work runs through Zambo, every step carries a verifiable receipt under AER-1, published as IETF Internet-Draft draft-zambo-aer1-26, and the acceptance state tells you at a glance which finished jobs are still missing their invoice. New users get 20 free calls per day, then they upgrade when the job needs more. For $0.99, put the next job on that footing and let the monthly sweep find nothing to forgive: get the Day Pass. A Day Pass covers 24 hours, no subscription. Ongoing use is the Zambo Pass at $29 a month or $290 a year, and $19 a month for $ZAMBO holders, which adds private handover links, your branding, and the approval record as PDF and JSON files.

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