A blank chat
Paste the prompt. Ask for the four lists. If the thread starts inventing customer names or a payment run, stop and paste the prompt again with the first line repeated: do not mark anything paid.
Synthetic books · one bottleneck
Harbourline Supplies is fictional. The invoices, the bank lines and the 30-day result are invented. The founding cohort has not run. The point is the process: find the delay, log it, decide what AI may draft, and keep a person on the amount.
The same instructions work in ChatGPT, Microsoft Copilot and Gemini. The tool does not clear the ledger, release a payment, or send the reminder.
These replies are worked examples written to those instructions. They are not transcripts from ChatGPT, Copilot or Gemini. Paste the prompt into the tool your organisation already allows, and compare.
F · Find
Harbourline Supplies is a fictional 36-person equipment distributor in Singapore. Customers pay by GIRO, PayNow and transfer. The description on the bank line often leaves out the invoice number. The accounts assistant then hunts for the invoice and, when the books still show it open, writes a collection note from scratch.
On a week like this one, that loop is about six hours. About three hours go to matching. About two hours go to writing notes. About one hour goes to correcting a note that asked for money already received, or for a balance a credit note had already reduced.
L · Log the baseline
Customer legal names are already replaced with codes. There are no bank account numbers. That is the form in which this list may be pasted into a tool.
Download the synthetic books (.csv)
| Code | Document | Kind | Date | Due | Amount (S$) |
|---|---|---|---|---|---|
| C-014 | INV-1044 | Invoice | 12 Aug 2026 | 11 Sep 2026 | 4,280.00 |
| C-021 | INV-1061 | Invoice | 2 Sep 2026 | 2 Oct 2026 | 1,860.50 |
| C-044 | INV-1052 | Invoice | 20 Aug 2026 | 19 Sep 2026 | 3,140.00 |
| C-044 | CN-019 | Credit note | 2 Oct 2026 | — | −140.00 |
| C-033 | INV-1077 | Invoice | 18 Sep 2026 | 2 Oct 2026 | 640.00 |
| C-014 | INV-1088 | Invoice | 1 Oct 2026 | 31 Oct 2026 | 910.00 |
| C-052 | INV-1092 | Invoice | 8 Oct 2026 | 7 Nov 2026 | 2,750.00 |
| C-021 | INV-1099 | Invoice | 15 Oct 2026 | 14 Nov 2026 | 430.00 |
| C-061 | INV-1104 | Invoice | 22 Oct 2026 | 21 Nov 2026 | 1,588.00 |
| Line | Date | Description as it arrived | Amount (S$) |
|---|---|---|---|
| B-01 | 3 Oct 2026 | GIRO C014 AUG | 4,280.00 |
| B-02 | 9 Oct 2026 | PAYNOW 1860.50 REF 1061 | 1,860.50 |
| B-03 | 14 Oct 2026 | TRANSFER 640 | 640.00 |
| B-04 | 21 Oct 2026 | C052 PART 1500 | 1,500.00 |
| B-05 | 28 Oct 2026 | MISC 910.00 | 910.00 |
The control total, before any matching: documents S$15,458.50 minus receipts S$9,190.50 leaves S$6,268.00. A reply that does not land on that difference has dropped a row.
O · Screen the option
Eligibility is ordinary. The work repeats every week, the saving is staff time and fewer wrong notes, and the material can be reduced to codes. The exposure is a wrong balance sent to a customer. The control is a named reviewer. No new system is required.
W · Write the workflow, then run it
Use the tenant the company has already approved. A personal ChatGPT, Copilot or Gemini account is the wrong place for a real customer list. This demonstration uses codes only, so the paste itself contains no legal names and no account numbers.
You are helping an accounts assistant. Today is 30 October 2026. Do not mark anything paid. Do not send email. Do not change a figure. Suggest only. Documents (SGD). A credit note reduces the balance for that code. C-014, INV-1044, invoice, 12 Aug 2026, due 11 Sep 2026, 4280.00 C-021, INV-1061, invoice, 2 Sep 2026, due 2 Oct 2026, 1860.50 C-044, INV-1052, invoice, 20 Aug 2026, due 19 Sep 2026, 3140.00 C-044, CN-019, credit note, 2 Oct 2026, no due date, -140.00 C-033, INV-1077, invoice, 18 Sep 2026, due 2 Oct 2026, 640.00 C-014, INV-1088, invoice, 1 Oct 2026, due 31 Oct 2026, 910.00 C-052, INV-1092, invoice, 8 Oct 2026, due 7 Nov 2026, 2750.00 C-021, INV-1099, invoice, 15 Oct 2026, due 14 Nov 2026, 430.00 C-061, INV-1104, invoice, 22 Oct 2026, due 21 Nov 2026, 1588.00 Bank receipts still unmatched: B-01, 3 Oct 2026, GIRO C014 AUG, 4280.00 B-02, 9 Oct 2026, PAYNOW 1860.50 REF 1061, 1860.50 B-03, 14 Oct 2026, TRANSFER 640, 640.00 B-04, 21 Oct 2026, C052 PART 1500, 1500.00 B-05, 28 Oct 2026, MISC 910.00, 910.00 Return four lists: 1. Likely matches, and why. 2. Possible matches. Say what is missing. 3. Documents not yet due. Do not draft a chase for these. 4. One reminder only, for a code that is overdue, has no likely match waiting, and is stated after open credit notes. Reminder template, keep this shape: Subject: Invoice [number] — balance outstanding Hello, Our records show invoice [number] dated [date] still has a balance of S$[amount]. Please reply with the payment date, or tell us if a credit note should be applied. Harbourline Supplies Accounts Then add the control total: documents minus receipts. Documents net 15458.50 and receipts are 9190.50. If your remaining balance does not reconcile to the difference, say which row you dropped.
Paste the prompt. Ask for the four lists. If the thread starts inventing customer names or a payment run, stop and paste the prompt again with the first line repeated: do not mark anything paid.
The same rows already sit on two sheets. Ask Copilot in Excel to add Days past due with a formula you can see, and to put suggestions on a new sheet. It must not overwrite Amount, and it must not add a Paid column.
The formula to accept or reject is =MAX(0, DATE(2026,10,30)-D2) where D2 is the due date, and a blank due date stays blank.
In a company Google account, point Gemini at the Invoices and Bank tabs and give it the same four lists. In a personal Gemini chat, paste the prompt exactly as for ChatGPT. The place changes. The instruction does not.
| Receipt | Suggested document | Why |
|---|---|---|
| B-01 · S$4,280.00 | INV-1044 · C-014 | Same amount. The description has the code and “AUG”, which fits the August invoice. It does not contain the invoice number. |
| B-02 · S$1,860.50 | INV-1061 · C-021 | The amount matches, and the description contains 1061. |
| B-05 · S$910.00 | INV-1088 · C-014 | The amount matches the October invoice. C-014’s August invoice is already the likely match for B-01. The description has no code, so this stays likely rather than certain. |
| Receipt | Candidate | What is missing |
|---|---|---|
| B-03 · S$640.00 | INV-1077 · C-033 | The amount is unique. The description has no code and no invoice number. Amount alone is not a match. |
| B-04 · S$1,500.00 | INV-1092 · C-052 | The description says part payment. The invoice is S$2,750.00, so S$1,250.00 stays open. Due 7 November, so there is no chase on 30 October. |
INV-1088 if B-05 is accepted, the INV-1092 balance of S$1,250.00, INV-1099 (S$430.00) and INV-1104 (S$1,588.00). No reminder.
C-044, INV-1052, is overdue and has no bank line. Credit note CN-019 for S$140.00 is still open on the same code. The balance to state is S$3,000.00.
Subject: Invoice INV-1052 — balance outstanding Hello, Our records show invoice INV-1052 dated 20 August 2026 still has a balance of S$3,000.00, after credit note CN-019 for S$140.00. Please reply with the payment date, or tell us if a further credit note should be applied. Harbourline Supplies Accounts
Control total: S$15,458.50 − S$9,190.50 = S$6,268.00. If B-01, B-02, B-04 and B-05 are later accepted and B-03 is held, the open items are S$3,000.00, S$640.00, S$1,250.00, S$430.00 and S$1,588.00, which sum to S$6,908.00. The S$640.00 gap is the held line.
Paste only the invoice numbers and the amounts, and leave out the bank lines, the credit note and the as-at date. The draft then chases INV-1044 and INV-1061, which are the likely matches already in the bank, and it asks C-044 for S$3,140.00. That is the hour spent correcting last month’s notes. The lists, the credit note, the date, and the line “do not mark anything paid” are the controls.
The person, before anyone relies on it
While B-03 and B-05 stay held, S$1,550.00 of receipts are still unexplained and the open balance is S$7,818.00. Accepting both would bring the open balance back to the control difference of S$6,268.00.
Monday’s step, on a real file: export ten open documents and the unmatched receipts, replace legal names with codes, paste into the approved tool, and tick or reject every line. Time the matching. Count how many drafts you change before sending.
30 · Review and decide
The figures below are synthetic. They describe this fictional pilot, not a client.
| Measure | Baseline | Over 30 days |
|---|---|---|
| Hours on this loop | About 6 a week | The messy match fell from about 12 minutes to about 4 |
| Suggested matches | None. Each line was searched by hand. | 22 suggested. 18 accepted, 3 rejected, 1 corrected. The correction was a part payment the draft had treated as full. |
| Reminders | 12 sent last month, 3 of them wrong | 9 drafted. 8 sent after the balance was checked. 1 held. |
| Ledger and mailbox | The assistant posted and sent | The tool posted nothing and sent nothing |
Scale the suggestion list and the draft reminder. Keep the named reviewer on the amount, the customer and the send.
The hours that came back are capacity. They are not profit, unless the company actually spends less.
A shorter fictional finance pilot sits in the case gallery. This page is the worked process behind that kind of result. Check a different bottleneck if the delay in your company is not the invoice and the unpaid balance.