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Error - Purchase Invoice Posting

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Posted on by Dharmesh

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Dear Experts,

I am facing an issue while posting a Purchase Invoice. I have noticed that this error appears only sometimes. On certain occasions, it stops me from posting the Purchase Invoice, and at other times, it does not appear and the posting goes through successfully.

I tested this in two different projects. In the first project, the system did not allow posting and showed the error. After a few days, I tried again, and at that time the error did not appear, and the posting was successful. The same situation occurred in the second project. In the Production environment, I have been unable to post the Purchase Invoice for the last 15 days because the error consistently appears. However, in the Sandbox for the same project, the error appeared initially, but after two days, it stopped showing and the posting was allowed.

If anyone has a solution or guidance for this issue, I kindly request your support.

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Dynamics 365 Business Central

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OussamaSabbouh 11,612 Super User 2026 Season 1 on at

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Hello,

This error simply means one of the system-generated posting lines ended up with the wrong sign, usually because of rounding, discounts, item charges, or custom extensions. That’s why it appears only sometimes, it depends on the specific invoice values.

The posting routine creates hidden Gen. Journal Lines.

If one of them should be negative but becomes positive, BC blocks posting and shows this message.

It happens with: rounding, currencies, discounts, negative lines, or extensions modifying posting.

Sandbox vs Production differences come from setups or extensions behaving differently.

Check the below:

Remove invoice discounts and test again.

Remove item charges.

Try posting without VAT.

Check currency rounding precision.

Temporarily disable custom extensions.

One of these usually reveals the cause.

Regards,
Oussama Sabbouh

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Jainam M. Kothari 15,721 Super User 2026 Season 1 on at

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Hello,

The error “Amount must be negative” typically occurs when Business Central expects a negative amount (e.g., for a credit memo or reversal) but finds a positive value, often due to document type, VAT/discount adjustments, or custom logic.

It appears inconsistently because factors like currency rounding, posting setup, or extensions can influence validation differently across environments.

To resolve it, verify the document type and sign logic, check posting groups and VAT setup, and temporarily disable custom extensions to isolate the issue; if needed, use debugging to trace the CheckAmount validation in the posting codeunit.

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RockwithNav 8,866 Super User 2026 Season 1 on at

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If you will pos the entire screenshot then we can point exactly but just to let you know, if amount is going in negative then purchase invoice wont be eligible for posting as the payables will get impacted. You purchase invoice expects to be the amount in positive only, -ve means Credit Memo. On journals you can use any sign -ve +ve that would be fine.

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Dharmesh 344 on at

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Dear All

I have mentioned the transaction details below.

The first line includes the GST amount, and the second line excludes GST.

I processed the same transactions last month with the exact same setup, and at that time, I did not face any errors — the posting completed successfully. Even in the Sandbox environment, the error has now disappeared automatically and the posting is going through without any issues. However, in the Production environment, I am still facing the error, and I am unable to identify the source or reason for it.

Kindly advise.

Purchase Invoice Line :

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