# How to stop paying a purchase invoice twice in Business Central

Before you enter a purchase invoice in Business Central, search the vendor's bills for the same number or amount. Use one reference format and check the payment journal and Suggest Vendor Payments for repeats.

Duplicate payment is when the same supplier invoice is entered or paid more than once. It often happens when an invoice arrives by two routes.

## Before you start

- Purchases & Payables Setup access

## The Business Central way

Where to find it: Purchases & Payables Setup > Ext. Doc. No. Mandatory

1. In Purchases & Payables Setup, select Ext. Doc. No. Mandatory. Business Central then will not post a purchase invoice or credit memo without the vendor's number.
2. Enter the vendor's number in the Vendor Invoice No. field on the purchase header. On a general journal line, use the External Document No. field. The line must have the document type Invoice, Credit Memo or Finance Charge Memo and the account type Vendor.
3. Before you post, search the posted invoices and the vendor ledger entries for that number.
4. Check the vendor and the amount as well as the number.

## Limits in Business Central

- The setting makes the number compulsory. The sources do not describe it as a check for repeats, so search for repeats yourself before posting.
- Your Reference can hold the number instead, and you can search it in posted documents. It is not available on journal lines.

## Good to know in Business Central

- Your Reference is another field that can hold the number.

## The Pulsify way

1. Forward the supplier's invoice to Pulsify.
2. Pulsify compares the invoice number with punctuation and case ignored, plus the same vendor, invoice date or tax ID.
3. It checks other Pulsify documents and active bills in Business Central.
4. A possible duplicate is flagged. Open the match, then reject or approve anyway.

Pulsify connects to Business Central. We set up the connection for you.

What Pulsify does not do here:

- Pulsify flags. You decide.
- A duplicate with a quite different invoice number may not be found.

## Example in Business Central

Example Plumbing Supplies sends invoice INV-5521 by email and again by post. The first is posted as a purchase invoice.

- Posted purchase invoice, Vendor Invoice No. INV-5521: $1,320.00 (Posted)
- Second copy, searched by INV-5521 in vendor ledger entries: $1,320.00 (Found before posting)

You find the posted entry in the vendor ledger entries and do not post the second copy. Paying both would cost $1,320.00 twice.

## Common mistakes

- Leaving Ext. Doc. No. Mandatory off, so invoices post with no vendor number.
- Typing an internal reference in Vendor Invoice No. instead of the vendor's own number.
- Entering a vendor invoice on a general journal line and a purchase invoice for the same bill.
- Searching only by the vendor's number when it has been put in Your Reference.

## Common questions

### Does Business Central stop me posting the same vendor invoice twice?

Turning on Ext. Doc. No. Mandatory makes the vendor's number compulsory before an invoice or credit memo posts. The documentation does not describe it as a duplicate check, so search posted documents and vendor ledger entries for the number first.

### Where do I find an invoice I posted by vendor number?

Search posted purchase documents by the number, or search the vendor ledger entries. Both show the external document number.

### Does the setting apply to journals too?

Yes. It covers the External Document No. field on general journal lines with the document type Invoice, Credit Memo or Finance Charge Memo and the account type Vendor.

### What does Pulsify check?

The invoice number with punctuation and case ignored, plus the same supplier, invoice date or tax ID.

## Sources

- https://learn.microsoft.com/en-us/dynamics365/business-central/purchasing-ext-doc-no
- https://learn.microsoft.com/en-us/dynamics365/business-central/purchasing-setup-purchasing

Source: https://www.pulsify.tech/how-to/stop-paying-a-bill-twice-in-business-central/ (last checked 2026-10-19)