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Unusual Monthly Billing

Marsha Galicia avatar
Written by Marsha Galicia
Updated yesterday

XBert Type: Standard

Accounting Software: Xero, MYOB, QuickBooks

Country Restriction: AU only

Risk Type: Unusual Risk

Business Function: Purchases

Overview

The "Unusual Monthly Billing" XBert detects supplier billing patterns that differ significantly from previous months. If a supplier’s total billed amount for a recent month is unusually high or low based on historical trends, this alert is triggered to help you validate its accuracy and avoid incorrect payments.

What it does

This XBert analyses Paid and Raised bills and identifies statistical outliers in monthly totals for each supplier. If a supplier has billed you significantly more or less than usual in a given month, the alert prompts you to review those bills to ensure they are correct and expected.

How it works

XBert groups your bill data by:

  • Supplier name and ID

  • Bill due date (used to determine the billing month)

  • Currency (AUD only)

For each supplier, it:

  • Calculates the monthly total billing amount

  • Flags outliers using the interquartile range (IQR) method, where months falling outside 1.5 × IQR are considered statistically unusual

  • Only includes Paid and Raised bills

  • Excludes the current (incomplete) month and focuses on outliers within the last 3 months

Example/Use Case

Higher than usual: Your business has consistently received monthly bills from XYZ Print Co. ranging from $1,500–$2,000. This month, a bill for $6,000 appears. XBert flags this for review — it could be due to a service bundle, a one-off project, or a mistake (like double billing).


Lower than usual: Another supplier, TechParts Pty Ltd, usually bills you $3,000/month. This month, the amount is only $300. While it might be legitimate, it could also mean a missed bill or incorrect entry. Reviewing it ensures that essential goods or services weren't accidentally left out.

Accounting software

All major Australian-compatible accounting software (e.g., Xero, MYOB, QuickBooks Online).

Which countries it supports

Australia only.

Processes

This alert falls under the ‘Purchases (AP)’ category and helps you monitor irregular supplier charges. To resolve this issue:

  • Open the Purchase records for the flagged supplier.

  • Review the bills due for the month in question.

  • If the bill is incorrect, void it and notify the supplier to reissue it.

  • If the bill is valid, you may file the alert to close it.

  • Compare it to prior months to confirm any legitimate changes in supplier charges or volume.

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