MosoFin skill · duplicate-invoice-detection · learning guide

From one invoice number entered twice to the test the scan cannot run

This page shows how the skill finds a bill your business entered or paid twice, one level at a time. It starts with one invoice number that appears twice. It ends with the one rule the scan cannot run here. The page quotes every rule from the skill itself. It also works every number in front of you.

The rules are the skill's ownThe page quotes each rule word for word, with the file and section it comes from.
Outside sources back the factsThey are a fraud study, QuickBooks help, a US Census Bureau paper, the IRS, the FBI and the GAO. Each one has a number and a link.
The page shows the mathOpen "Check it yourself" on any level. Follow every line on a calculator.
Your numbers, your checkAt the end, enter the clusters from your own scan. The page totals the exposure the same way.
Rule: quoted from the skill Fact: from a cited authority, numbered like 1 Example: made-up figures, calculated in full
How it thinks

Fourteen rules the whole skill runs on

Every level below applies one or more of these rules. The examples use one company, Northbrook Trading. The scan covers 1 July to 31 October, and September is the month under review. It reads 1,284 bills from 212 vendors, 1,197 bill payments and 14 open vendor credits. The sensitivity is Standard, and the Rule 3 window is 7 days.

Learning path

Six levels, from simple to complex

Check it yourself

Put in your own scan

Enter up to six clusters from your own scan, or load an example. For each cluster, pick the rule that matched, the amount per record, the record count and the paid status. Then pick the sensitivity. The page shows which clusters that setting flags and totals the exposure. The page sends nothing anywhere.

Sensitivity
Clusters

The page counts one record in each cluster as the real bill. So the exposure of a cluster is the amount per record × (records − 1). Standard flags High and Very High. Strict adds Medium. Permissive flags Very High only. A credit cluster is never exposure. The page shows it as money owed to you, whatever the sensitivity. Rule 7 never runs here, so a Rule 7 cluster adds nothing. The "Northbrook, July to October" preset holds the six clusters from the levels. Under Standard: $1,250.00 + $4,860.00 + $3,200.00 = $9,310.00 flagged. Under Strict: $9,310.00 + $980.00 + $950.00 = $11,240.00.

Using it

What it asks, needs and gives back

Asks firstDo you want to use MosoFin, or upload the data yourself? Which period should the scan cover? Which suppliers bill the same amount every month on purpose? Strict, Standard or Permissive, and what window for Rule 3? Who runs the bank-account test, Rule 7, and how often? Do you have results from an earlier scan, with clusters already cleared?
NeedsThe skill needs the AP register for the whole window, with vendor, invoice number, date, amount and status. It needs the payment register, with the date and the method of each payment. The vendor master with inactive records and the open vendor credits make the result better.
Gives backThe skill gives back seven sheets. They are a summary, the flagged clusters, the record detail, the vendor aliases to merge and the recovery plan. The last two are the rules-run sheet and a coverage sheet. Unpaid duplicates come first. The skill asks before it makes an Excel file.
NeverThe skill never voids a record, never merges a vendor and never asks a supplier for money. It never defaults the period or the entity. It never reports Rule 7 as finding nothing. It never saves bank details or a suspicion attached to a named person.
Sources

Where every fact on this page comes from

The rules are the skill's own. The facts below come from six outside sources. They are a fraud examiners' association, QuickBooks Online help, a US Census Bureau research paper, the IRS, the FBI and the US Government Accountability Office. MosoFin checked each one on 27 October 2026 official source pages and reviewed the linked sources on 27 October 2026. Follow each link for the latest wording.

    Not backed by an outside authority. The ten rules, their order and their confidence levels are the skill's own. So are the 0.85 name-score threshold, the 7-day window, the three sensitivity settings and the seven output sheets. The page marks them as the skill's where they appear.