Rule of the week: Same Amount + Similar Vendor

The error, and why it happens

You're reconciling the payments run and something in the amount column repeats: $2,340.00, twice, twelve days apart. The vendor names don't quite match — one says "Sharp Electrical Services", the other "Sharp Electrical Pty Ltd" — so your eye slides past it. Different vendor, must be a different job. Except it isn't. It's the same sparky, who invoices under his trading name half the time and his company name the other half, and whoever entered the second payment created a new supplier card rather than searching for the existing one.

This is the quieter cousin of the classic duplicate payment. The classic one is easy to catch because the vendor name is identical and the invoice number is a giveaway. This one survives because the name is almost the same — a trading name versus a legal name, "P/L" tacked on or dropped, a missing middle initial, a supplier who rebranded mid-year and nobody merged the contact card. Multiply that across a few hundred vendors and a few thousand payments a year, and it's not rare. It's just invisible to a name-match filter.

A worked example

• 14 March: payment of $4,875.00 to "Coastal Plumbing & Gas"
• 2 April: payment of $4,875.00 to "Coastal Plumbing and Gas Pty Ltd"

Nineteen days apart, identical amount, obviously the same underlying invoice paid twice through two supplier cards that were never reconciled to each other. Nothing in a standard duplicate check catches this, because a standard check usually requires an exact vendor name match. Here the names are close enough that a human reading both would recognise them as the same business in about two seconds — but a system doing literal string comparison won't.

How to find it manually

You need a payments export with date, amount and vendor name — bank rec report or accounts payable transaction listing, whichever is complete.

1. Sort by amount, not by vendor or date. This is the step people skip, and it's the one that matters, because the whole point is that the vendor field can't be trusted to group the pair together.
2. Scan for repeated amounts. Round or unusual dollar figures are the easiest tells — a generic $110.00 GST-inclusive amount will throw up genuine coincidences, so weight your attention toward specific, less common figures like $4,875.00 or $2,340.00.
3. For each repeat, read the vendor names side by side. You're checking for trading name vs legal name, abbreviations, punctuation differences, or a supplier who appears twice because someone fat-fingered a new contact card instead of searching.
4. Check the date gap. A repeat six months apart is more likely a genuine second job than a duplicate. Inside a month or two, treat it as a candidate.
5. Pull both source invoices before you conclude anything — a genuine second payment with a coincidental amount match is common enough that you shouldn't reverse a payment on pattern-matching alone.

Honestly: this takes a working knowledge of your vendor list — which suppliers have multiple trading names, which have restructured — and a decent chunk of time on anything larger than a small file. On a file with a few thousand payments a year, a careful pass is a multi-hour job, and it's easy to miss a pair if the amount happens to be a common one.

FAQ

How do I detect duplicate payments to vendors with slightly different names but the same amount? Sort your payments by amount rather than vendor, then manually compare vendor names for near-matches — trading name vs legal name, punctuation, abbreviations — within a window of a month or two either side. There's no way to automate the name comparison in a spreadsheet without fuzzy-matching logic, so on a manual pass you're relying on your own eye and your knowledge of the vendor list.

What counts as a "similar vendor" for duplicate payment purposes, rather than just a similar amount? Names that a human would recognise as the same underlying business despite not being character-for-character identical — trading name versus registered name, "and" versus "&", a dropped or added entity suffix. Two genuinely different suppliers who happen to charge the same amount for unrelated jobs are not a match, however tempting the coincidence looks.

How the rule does this automatically

It will occasionally flag two genuinely different vendors whose names happen to score above the similarity threshold on a coincidental amount, and it won't catch a duplicate if the second payment lands more than 45 days after the first or if the vendor name has changed enough to fall under 85% similarity — a full rebrand, for instance. Rule DUP-003 runs a similarity score across vendor names rather than requiring an exact match, so it catches the trading-name and punctuation variants that a stricter same-vendor check (DUP-002) misses, flagged at medium severity for a human to confirm.

Finanomaly is currently waitlisted.