Duplicate invoice check prompt: free ChatGPT template
Updated · By Robert Breen
Use this before a payment run, with the bills about to be paid and a list of recent payments. Duplicates happen in ordinary ways: a vendor emails an invoice and also mails it, someone keys INV-1043 once as "1043", or a statement gets entered as a new bill.
AI is good at spotting near-matches in a long list and bad at knowing which are fine, like a subscription that should repeat. So this prompt rates each finding Likely duplicate, Check or Expected repeat, and leaves the decision to you.
The prompt
Copy it into ChatGPT (or Claude, Gemini or Copilot) and replace every [BLANK] with your own details. It uses the four parts from Prompt Writing 101: Role, Context, Task and Format.
Role: You are an accounts payable reviewer for [BUSINESS], looking for duplicate bills before payment. You flag; you don't decide. Context: Bills about to be paid: [BILLS TO PAY]. Bills paid in the last [LOOKBACK]: [PAID BILLS]. Charges we expect to repeat: [EXPECTED REPEATS]. Task: Compare every bill to pay against the others and the paid list. Flag pairs with the same vendor and amount, invoice numbers that match once spaces, dashes, prefixes and leading zeros are ignored, and the same amount and date under slightly different vendor names. Rate each pair Likely duplicate, Check, or Expected repeat (only for listed repeats), with a short reason. Change nothing. Format: A table: bill to pay, possible match, rating, reason. Then one line with how many bills had no match. No emoji.
Fill in the blanks
[BUSINESS]- Your business name, or the client whose bills you are reviewing.
[BILLS TO PAY]- One per line: vendor, invoice number, date, amount, from your AP report.
[LOOKBACK]- How far back to compare, such as "60 days".
[PAID BILLS]- Bills paid in that window, same format.
[EXPECTED REPEATS]- Subscriptions, rent and other charges that recur, with their usual amount.
Example, filled in
A made-up example from the free lesson Build an AI Agent That Categorizes Business Expenses. Maple Street Bookkeeping is the made-up firm from the expense agent lesson, whose Expense Log includes Corner Office Supply at $64.18 and CloudLedger at $45.00, a monthly charge the agent says will show up again. Here the bookkeeper checks the firm's own payment run. Invoice numbers are made up.
Role: You are an accounts payable reviewer for Maple Street Bookkeeping, looking for duplicate bills before payment. You flag; you don't decide. Context: Bills about to be paid: Corner Office Supply, invoice 5521, Sep 22, $64.18. Corner Office Supply, invoice INV-05521, Sep 22, $64.18. CloudLedger, Oct 1, $45.00. Harbor Street Cafe catering, invoice 118, Oct 2, $212.00. Corner Office Supplies Inc., invoice 5530, Sep 29, $64.18. Bills paid in the last 60 days: CloudLedger, Sep 1, $45.00. Harbor Street Cafe, invoice 118, paid Sep 30, $212.00. Charges we expect to repeat: CloudLedger, $45.00 on the 1st of each month. Task: Compare every bill to pay against the others and the paid list. Flag pairs with the same vendor and amount, invoice numbers that match once spaces, dashes, prefixes and leading zeros are ignored, and the same amount and date under slightly different vendor names. Rate each pair Likely duplicate, Check, or Expected repeat (only for listed repeats), with a short reason. Change nothing. Format: A table: bill to pay, possible match, rating, reason. Then one line with how many bills had no match. No emoji.
What a good answer looks like
- 5521 and INV-05521 rated Likely duplicate: same vendor, date and amount, same number without the prefix and zero.
- Harbor Street Cafe invoice 118 rated Likely duplicate, since it was paid on Sep 30.
- Invoice 5530 rated Check: same amount, but a different number, date and vendor spelling.
- CloudLedger rated Expected repeat.
How to check it before you use it
An AI draft can sound right and still say something you never told it. Use the habit from the Reply Faster lesson: check every promise, name, date and number against what you gave it before anything goes out.
- Pull the documents for every Likely duplicate before deleting anything. Identical orders do happen.
- Look for "Corner Office Supply" and "Corner Office Supplies Inc." in your vendor list. Two records for one vendor keep duplicates coming back.
- Note what you removed and why, for your audit trail.
- Treat this as a second look, not a replacement for your system's duplicate warning.
Why this prompt works
Duplicates slip in when the same bill arrives two ways. A check after invoice approval and before money leaves accounts payable catches them, and the Expected repeat rating stops the AI crying wolf on every subscription.
Practice it in the free lesson
Build an AI Agent That Categorizes Business Expenses: Build an AI agent for Maple Street Bookkeeping that sorts business expenses into categories, writes a short note for each and saves them to Google Sheets — chat trigger, AI Agent, system prompt, model, memory, and the… You do every step yourself in a practice copy of n8n, and nothing touches your real accounts.
Also useful: AI Receipt Extractor: Receipts to Google Sheets with n8n
Terms used here
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