How do I find duplicate invoices in Excel?

Use COUNTIFS on vendor, invoice number and amount; any count above 1 is a duplicate.

How do I find invoices re-sent with a new number?

Compare invoices from the same vendor with the same amount within a few days of each other.

Should near-duplicates be blocked automatically?

No — recurring charges can legitimately repeat. Flag them for review.

How far back should I check?

At least three months, stacked together, because duplicates are often entered in different months.

How do I check whether a duplicate was paid twice?

Join the duplicates to the payments export on vendor and invoice number and count payments per invoice.

Have any suppliers billed us twice?

By the Analistable team · Updated 2026-10-07 · 3 min read

Look for two kinds of duplicate: exact (same vendor, invoice number and amount — usually entered twice) and near (same vendor and amount within a few days but different invoice numbers — often a re-sent invoice). A COUNTIFS on vendor + invoice + amount finds the first; a self-join on vendor + amount with a date window finds the second.

Part of our guide: How to answer questions across multiple spreadsheets

The data

Supplier invoices, September
Vendor	Invoice	Date	Amount
PackCo	P-881	2026-09-02	412.5
PackCo	P-881	2026-09-02	412.5
Fleet Ltd	F-19	2026-09-05	180
Fleet Ltd	F-20	2026-09-06	180
Print Hub	PH-7	2026-09-09	96

Exact duplicates

=COUNTIFS([Vendor], [@Vendor], [Invoice], [@Invoice], [Amount], [@Amount]) > 1

SELECT vendor, invoice, amount, COUNT(*) AS times
FROM bills
GROUP BY vendor, invoice, amount
HAVING COUNT(*) > 1;

Result
vendor	invoice	amount	times
PackCo	P-881	412.5	2

Near duplicates

SELECT a.vendor, a.invoice, b.invoice AS other_invoice, a.amount
FROM bills a
JOIN bills b ON a.vendor = b.vendor
            AND a.amount = b.amount
            AND a.invoice < b.invoice
            AND ABS(julianday(a.inv_date) - julianday(b.inv_date)) <= 7;

Result
vendor	invoice	other_invoice	amount
Fleet Ltd	F-19	F-20	180

F-19 and F-20 may both be genuine (two weekly deliveries at the same price) — near duplicates need a human check, not an automatic block.

Normalise first

Invoice numbers typed differently (“P-881”, “P881”, “p-881 ”) hide exact duplicates. Remove spaces, dashes and case before comparing.
The same supplier set up twice under slightly different names: group by bank account or VAT number as well as name.
Run the check before payment runs, not after — recovering a duplicate payment takes far longer.

Ask it in Analistable: “List supplier invoices with the same vendor and amount within 7 days of each other.” More on reconciling payables: three-way match.

In Google Sheets

Helper column E: =COUNTIFS(A$2:A, A2, B$2:B, B2, D$2:D, D2)
Duplicates:      =FILTER(A2:D, E2:E > 1)

Google Sheets' QUERY has no HAVING clause, so count with COUNTIFS in a helper column and filter on it. The same helper works in Excel.

Prevent it next time

Make vendor + invoice number a unique key in your accounts payable system, so the second entry is rejected.
Ask suppliers to send invoices to one mailbox only — duplicates often come from the same PDF sent to two people.

Normalise invoice numbers in one formula

Clean invoice =UPPER(SUBSTITUTE(SUBSTITUTE(TRIM([@Invoice]), "-", ""), " ", ""))
Key           =[@Vendor] & "|" & [@[Clean invoice]] & "|" & [@Amount]
Duplicate?    =COUNTIF([Key], [@Key]) > 1

“P-881”, “P881” and “p-881 ” all become P881, so the exact-duplicate check catches them. The combined key also works in older Excel versions: select the Key column and use Home › Conditional Formatting › Highlight Cells Rules › Duplicate Values for a visual check.

Value at risk in the example

September findings
Finding	Invoices	Amount at risk	Action
Exact duplicate	PackCo P-881 ×2	412.5	Pay once, void the second entry
Near duplicate	Fleet Ltd F-19 / F-20	180	Check delivery notes before paying

Of September's 1,281 in supplier invoices (412.5 + 412.5 + 180 + 180 + 96), 412.5 is a confirmed duplicate and up to 180 more needs checking. Sum these figures each month to show the value of the control.

Checking across files and periods

Duplicates often straddle months: an invoice entered in August and again in September never shows up in a single month's check. Stack at least the last three months of supplier invoices before running both queries, and add the payments export to see which duplicates were actually paid twice — those need a refund request, the others only a correction.

Troubleshooting

Common problems
Symptom	Cause	Fix
Hundreds of near duplicates	Fixed monthly fees (rent, subscriptions)	Exclude recurring vendors or widen to amount + description
Exact duplicates missed	Amounts differ by rounding (412.5 vs 412.50 as text)	Convert amounts to numbers and round to 2 decimals
Same supplier under two names	Duplicate vendor records	Group by VAT number or bank details

Frequently asked questions

How do I find duplicate invoices in Excel?: Use COUNTIFS on vendor, invoice number and amount; any count above 1 is a duplicate.
How do I find invoices re-sent with a new number?: Compare invoices from the same vendor with the same amount within a few days of each other.
Should near-duplicates be blocked automatically?: No — recurring charges can legitimately repeat. Flag them for review.
How far back should I check?: At least three months, stacked together, because duplicates are often entered in different months.
How do I check whether a duplicate was paid twice?: Join the duplicates to the payments export on vendor and invoice number and count payments per invoice.