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Correcting a posted invoice in Exact Online with AI

By Frank Woutersen · October 21, 2026 · 7 min read

TL;DR A processed invoice is a sales or purchase entry in Exact Online. Through Ledger Botje an AI assistant can change a line of it (VAT code, amount, GL account, cost centre, description) or delete it, and shows the entry before and after. If a VAT return has already been filed for the period, Exact Online may refuse the change and a credit note or correcting entry is still needed.

An invoice with the wrong VAT code, a cost on the wrong GL account, an empty line that was posted by accident: once an invoice has been processed, it feels as if only a journal entry or credit note can help. Often that is not necessary. A processed invoice is a sales or purchase entry in Exact Online, and its lines can be changed. Through Ledger Botje an AI assistant does that for you, with the entry before and after.

Draft, processed or declared: what is possible when?

Situation	What you do	Tool
Draft invoice, not yet processed	change the invoice itself	`sales_invoices_update`, `sales_invoices_update_line`, `sales_invoices_delete_line`
Processed sales invoice	change or delete the line of the sales entry	`financial_sales_update_line`, `financial_sales_delete_line`
Posted purchase invoice	change or delete the line of the purchase entry	`financial_purchase_update_line`, `financial_purchase_delete_line`
Period already in the VAT return, or Exact Online refuses	credit note or correcting entry	`financial_sales_create`, `financial_generaljournal_create`

Changing a VAT code on a posted invoice

The most requested case. A prompt:

"Sales entry 26700123 has VAT code 1 (9%) on line 2, that should be 2 (21%). Show me the lines first and then change it."

The assistant fetches the entry with financial_sales_get. It contains an id per line, and that is the key Exact Online needs. Then it calls financial_sales_update_line with the new vatCode.

There is a pitfall we ran into in September 2026: on an update Exact Online does not take the VAT percentage over from the new code. The line keeps its old percentage, and Exact Online refuses with an invalid VAT percentage message, even if you send the correct VAT amount. The tool therefore looks up the percentage for every new VAT code in the VAT codes of the administration (financial_vatcodes_list) and sends it along. The tool itself refuses an unknown or blocked code, before anything goes to Exact Online.

Changing the amount, GL account or cost centre

The same tool also changes amount (excluding VAT, positive as the entry shows it), glAccountCode, costCenter, costUnit, description and notes. Only what you pass goes to Exact Online; the rest of the line stays as it is.

Exact Online calculates the receivable or payable line and the VAT line itself. The tool does not change those: only the lines you see on the invoice can be adjusted.

Deleting a line

You remove an empty or duplicate line with financial_sales_delete_line or financial_purchase_delete_line. The tool only checks that the line exists, is in this administration and belongs to the right journal. Whether the deletion is allowed is up to Exact Online: the tool passes on the Exact Online message. The response contains the deleted line and the lines before and after.

Check afterwards

After every change the connection reloads the entry and returns before and after. With a new VAT code, look in particular at the VAT amount (amountVATFC). If it differs, ask the assistant to pass the correct amount:

"The VAT amount on line 2 should be 21 euros. Adjust that and show me the entry once more afterwards."

When not to do it this way

The VAT return has already been filed. Exact Online may refuse a change in a declared period. Then a correction in a later period is still needed; see preparing the VAT return with AI.
The customer already has the invoice. Changing an entry line adjusts your administration, not the document the customer already has. If the customer needs a corrected invoice, a credit note with a new invoice is the proper way. A negative line amount in financial_sales_create creates a credit note.
Write permissions. Changing and deleting are write actions: you need Advanced and writing must be enabled. A firm can switch that off for colleagues.

Exact Online without and with an AI connection

	Exact Online without an AI connection	Exact Online with Ledger Botje (MCP)
Wrong VAT code on a processed invoice	find the entry, open the line, change code and percentage, or a journal entry	one request, percentage included automatically
Removing an empty line	open the entry and delete the line	in the same request, with the lines before and after
Check	look back yourself	`before` and `after` in the answer

Also read speeding up the month-end close with AI and finding duplicate invoices. All entry tools are in the tool catalogue.

Frequently asked questions

Can I still change a processed invoice in Exact Online?

Not the invoice itself, but often the entry it produced. Through Ledger Botje an AI assistant changes a line of the sales or purchase entry: VAT code, amount, GL account, cost centre, cost unit, description or notes. Whether Exact Online allows it depends among other things on the VAT return for that period.

Why does Exact Online refuse a new VAT code with an invalid VAT percentage message?

On an update Exact Online does not take the percentage over from the new VAT code: the line keeps its old percentage. Ledger Botje therefore looks up the matching percentage for every new VAT code and sends it along. The tool itself refuses an unknown or blocked code, before anything goes to Exact Online.

Is the VAT amount recalculated?

Always check it. The tool returns the entry before and after the change. If the VAT amount is wrong after a new VAT code, the assistant can still pass the correct VAT amount.

When do I still need a credit note or journal entry?

When Exact Online refuses the change, for example because the period is already in a VAT return, or when the invoice has already been sent to the customer and the customer needs a corrected document. Changing an entry line adjusts the administration, not the document the customer already has.

Frank Woutersen

Frank Woutersen is the founder of Ledger Botje and writes about AI, MCP and Exact Online. He helps businesses manage their administration smarter with AI assistants.