# Duplicate invoice checks in Business Central for manufacturers

Business Central covers part of duplicate invoice checks on its own. Month-end volume hides duplicates. A bill sent twice in the last week is easy to approve twice.

## Why it matters for manufacturers

- Plants may receive the same invoice by email, post and portal. Each plant may then enter it.
- Recurring bills such as gas rental and maintenance contracts have the same amount each month, so a repeat looks normal.

## For manufacturers in Business Central

- Turn on Ext. Doc. No. Mandatory so every subcontractor invoice carries the supplier's invoice number in Vendor Invoice No.
- Subcontractors may bill the operation and then bill transport and packaging separately as item charges. Use clear invoice numbers on each so a search by external document number shows them as separate documents.
- The help does not confirm that posting stops on a repeated number.

## Rules that matter for manufacturers in Business Central

- A supplier must give a tax invoice for a taxable sale above $82.50 including GST. Hold a rental bill that arrives from a statement with no tax invoice.
- Business Central keeps ABN on the Vendor card. Vendors with no ABN can have withholding tax calculated, which covers the 47% withholding rule.
- Gas rental and maintenance contracts repeat each month. Compare the date range on the invoice, not only the number.

## What Business Central does on its own

Business Central can make the vendor's invoice number mandatory with Ext. Doc. No. Mandatory and lets you search posted invoices and vendor ledger entries by that number.

- Search for repeats yourself before posting, and check the vendor and amount as well.

Vendor ledger entries keep the number after posting.

What you need and the setup steps: https://www.pulsify.tech/duplicate-invoice-checks-for-business-central/

## Example

Example Industrial Gases bills monthly cylinder rental of $1,240 ex GST on invoice 7741. Plant 2 enters it from the emailed PDF. Head office enters it again from the supplier statement.

- Plant 2 purchase invoice, Vendor Invoice No. 7741: $1,240.00 (First entry)
- Vendor ledger entries searched by External Document No. 7741 (Finds the first entry before head office posts)
- Head office purchase invoice, Vendor Invoice No. 7741: $1,240.00 (Not posted, because the search found a repeat)

The head office clerk deletes the second invoice. Because the help does not confirm a stop on a repeated number, the search before posting is the control.

## Common mistakes

- Using Your Reference for the supplier's invoice number. The search then runs on the wrong field.
- Searching posted purchase invoices only. A bill still in an open document is not there yet.
- Assuming a repeated number is blocked at posting. The help does not say so.

## Step-by-step guides for Business Central

- How to stop paying a purchase invoice twice in Business Central: https://www.pulsify.tech/how-to/stop-paying-a-bill-twice-in-business-central/

## What Pulsify adds

Pulsify checks every invoice for a duplicate, including bills keyed straight into Business Central, and asks before approval. Pulsify connects to Business Central. We set up the connection for you. More: https://www.pulsify.tech/duplicate-invoice-checker/

## Common questions

### How do I avoid paying a subcontractor twice in Business Central?

Make the vendor invoice number mandatory with Ext. Doc. No. Mandatory and search vendor ledger entries by that number before posting. The help does not confirm a stop on a repeated number, so also check vendor and amount.

### Why do manufacturers get duplicate bills?

The same bill arrives through several routes and several people enter it. Month-end rush makes it worse. Agree one inbox and one person per supplier, then check supplier, amount and date.

### Where do I search for a number already used?

Search posted purchase invoices or open vendor ledger entries and filter on the External Document No. Do it before you post a new invoice from the same vendor.

## Sources

- https://learn.microsoft.com/en-us/dynamics365/business-central/purchasing-ext-doc-no
- https://learn.microsoft.com/en-us/dynamics365/business-central/subcontract-item-charges
- https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/tax-invoices

Source: https://www.pulsify.tech/duplicate-invoice-checks-in-business-central-for-manufacturers/ (last checked 2026-10-19)