Supplier Invoice Automation with Power Automate

Monday morning. The accounting mailbox holds forty invoices. Someone opens them one by one, renames the PDF, copies the amount, the supplier and the due date into a spreadsheet, emails the department head for approval, then forwards the whole pile to the accountant at month end. One invoice in twenty gets lost along the way, and you find out when the supplier chases you.

That whole chain can be replaced by a Power Automate flow that lives inside your Microsoft 365. Here is how it works, what stays in human hands, and the three mistakes that get expensive if you skip them.

Supplier invoice automation starts with a shared mailbox

Everything begins with a single address, something like invoices@yourcompany.com, that you give to every supplier. The flow triggers on each email received in that shared mailbox. It detaches the attachment, files it in a SharePoint library under a clean name (date, supplier, number) and creates a row in a list or a Dataverse table. That row is your invoice register.

The original email is never deleted. It is marked as read and moved to a "Processed" subfolder. The day an invoice goes missing, you find it in ten seconds, with proof of the date it arrived.

AI Builder reads the invoice: amount, supplier, due date, number

AI Builder ships a prebuilt invoice processing model. You hand it the PDF, it returns the supplier name, invoice number, invoice date, due date, net, tax and total amounts, with a confidence score for each field. It works on invoices it has never seen, with no training on your side.

AI Builder is paid for in Copilot credits, a few cents per invoice page, to be checked against Microsoft's current price list; the credits included in some licences disappear on 1 November 2026, so do not count on them. For a company handling a few hundred invoices a month, this is not the line item that will worry you.

The decisive part is the human check at a glance. The screen shows the PDF on the left and the extracted fields on the right, with low-confidence fields highlighted. The person confirms in ten seconds instead of retyping for three minutes. You do not remove the check, you make it fast.

An approval route that depends on the amount

Once the fields are confirmed, the flow applies your rules. Below a first threshold, the head of the relevant department approves. Above it, the managing director or the finance director joins in. These thresholds and approvers live in a SharePoint list you edit yourself, without reopening the flow. Recurring invoices tied to a known contract (rent, subscriptions, insurance) skip approval and only trigger a notification.

Approval happens in Teams through Power Automate approvals: one card, two buttons, a comment field. If nobody answers within three days, the flow sends a reminder. After two reminders, it escalates. An invoice never sits blocked without someone knowing.

Hand-off to accounting and reminders before the due date

Once approved, two things happen. First, the invoice goes to accounting: through your accounting software's connector when one exists, otherwise into the folder shared with your accountant, with a monthly summary generated by the flow. Second, the flow schedules a reminder one week before the due date for whoever runs the payments.

A simple dashboard completes the picture: what is awaiting approval, what is due this week, what is overdue. That is the core of our Supplier invoices without retyping template, which we adapt to your thresholds and your chart of accounts.

The classic mistakes: duplicates, scanned PDFs, VAT

• Duplicates. A supplier sends the invoice twice, or attaches it to their payment reminder. Before creating a row, the flow compares supplier, number and amount with the register. If the invoice is already known, it files the email without creating anything and flags it.
• Scanned PDFs and photos. Reading is less reliable on a crooked scan or a phone picture. Confidence scores drop, and the invoice goes to a full manual check. Ask your suppliers for native PDFs; most of them will oblige.
• VAT. The model reads amounts, it does not judge whether they add up. Add a simple check: net plus tax must equal the total, otherwise flag it. Special cases (reverse charge, exemptions, multiple rates) stay with your accountant.
• Emails with no attachment. Some suppliers send a download link. Plan a "handle manually" queue rather than a flow that fails silently.

Where to start? Count one month of invoices, list who approves what and from which amount, and create the shared mailbox. With those three things, a two to three day scoping is enough to fix the scope, and the build is then delivered at a fixed price set during scoping. If you would rather talk first, a thirty minute call is enough to see whether your case fits.