Invoice Processing Automation Inbox to approved in the ERP, exceptions to a person
Supplier invoices are in the accounting system the day they arrive, matched to the order, with one tap to approve.
- Installed for you · one-time$249
- Run for you$297/month
- Custom build · this process$5,000–9,000 one-time
- Starts whenGmail / Outlook trigger on the AP inbox + portal polling
Covers up to 1,000 invoices a month, one ERP and one AP inbox. Multi-entity, multi-currency approval matrices, or ERPs without an API are a custom build. Custom builds start at $2,000 site-wide; this band is for this process and its integrations.
Invoice Processing Automation is an automation Agentmelt installs in your own tools. The free template is a file you import yourself; the kit ($49) adds the setup guide and prompts. Installed for you costs $249 one-time and is live within two working days of access, with a recorded walkthrough and 30 days of fixes. Run for you costs $297/month, with setup and maintenance included. A custom build of this process is $5,000–9,000 one-time; custom builds start at $2,000 site-wide. No call is needed for any option. Written by Max Zeshut; last revised 2026-09-21.
Reference stack: Claude + n8n. Node names are on each step; the file is under the template.
Founder at Agentmelt
Reviews every build before it goes live; the workflow escalates to a person, never past one.
What is invoice processing?
Invoice processing automation takes the supplier invoice from wherever it arrives — an email attachment, a portal, a scan — extracts every field with a confidence score, validates the totals and checks for duplicates and changed bank details, three-way matches it against the purchase order and the receipt in the ERP, routes exceptions and approvals to the right person on their phone, and posts the approved invoice to NetSuite, Xero, QuickBooks or Sage with the coding and the trail. Clean matches within policy approve themselves; everything else has a named approver. Accounts payable handles exceptions instead of keying, and supplier status questions are answered from the ERP.
- Invoices get paid late when the one person who keys them in is away.
- The same invoice was paid twice and nobody noticed until the supplier said so.
- Approvals wait for someone to open the ERP; the cycle is three weeks.
- A changed bank detail on an invoice went through, and it was fraud.
- AP spends the afternoon answering “has our invoice been paid?”.
If two of these are yours, this is the process to look at first. Free audit — or read on.
What it looks like once it runs.
Invoice processing automation takes the supplier invoice from wherever it arrives — email attachment, portal, scan — extracts every field, validates it against the PO and the receipt, routes it to the right approver with the exceptions highlighted, and posts it to the ERP coded and ready to pay. Accounts payable handles exceptions instead of keying.
- 9:04 A PDF lands in the accounts-payable inbox. Supplier, dates, lines, totals and bank details are read off it.
- 9:05 Totals are checked, duplicates caught, and the invoice is matched to the purchase order and the delivery.
- 9:06 A clean match approves itself within policy; a mismatch goes to the buyer with the exact difference; finance gets one tap in Slack.
- 9:07 The approved invoice is posted to the accounting system with the trail attached.
- Later A supplier asking about payment gets an answer from the system's own record.
AP staff key invoices by hand, chase approvers by email, and discover duplicates and mismatches at month end. Suppliers call about payment status. Early-payment discounts are missed because approval took three weeks.
Invoices are in the ERP the day they arrive, three-way matched where a PO exists, coded from history where it does not, and approved on the phone. Duplicates are caught before posting. Cycle time drops from weeks to days, and the AP team's work becomes exceptions and supplier relationships.
Trigger, then 8 steps.
Seven of the eight steps run without anyone. Step 06 waits for a person; clean matches skip it.
Gmail / Outlook trigger on the AP inbox + portal polling
Capture the invoice
PDF, image or e-invoice attachment saved to a document store with the email metadata; non-invoice attachments are classified and filed elsewhere.
Extract fields
Supplier, invoice number, dates, line items, quantities, unit prices, tax, totals, PO reference and bank details, with a confidence per field. Multi-page and multi-currency handled.
Validate and detect duplicates
Totals foot, tax is arithmetically right, supplier exists (or is flagged as new), bank details match the master (change = fraud alert), and no invoice with the same supplier + number + amount exists.
Match to PO and receipt
Three-way match against the ERP: PO lines, quantities received, prices within tolerance. Non-PO invoices are coded by the agent from supplier history and GL rules.
Route exceptions and approvals
Clean matches auto-approve within policy limits; mismatches go to the buyer with the specific difference; non-PO invoices go to the cost-centre owner; new suppliers go to procurement for onboarding.
Approve on the phone
Approvers get the invoice summary and the exception in Slack or email with approve/reject/query buttons; reminders escalate after the SLA.
Post to the ERP
Approved invoices are created in NetSuite, Xero, QuickBooks, Sage or SAP with coding, attachments and the approval trail; payment runs pick them up.
Supplier status replies
Supplier emails asking about payment status are answered from the ERP data (received, approved, scheduled for date) so AP stops fielding calls.
In the ERP, coded and ready to pay
Invoices are in the ERP the day they arrive, three-way matched where a PO exists, coded from history where it does not, and approved on the phone.
One decision, at step 06. Seven steps ran without you.
Each pattern page explains it in plain words and lists every automation that uses it.
The template is built on n8n (how the n8n AI Agent node works); the same steps run on Make, Zapier or plain code. The tool is chosen to fit your accounts, you own the result, and the template comes in all three formats.
Data it touches
- AP inbox and supplier portals
- ERP: POs, receipts, supplier master, GL, approval policy
- Historic coding for non-PO invoices
- Bank-detail master for fraud checks
Guardrails
- Bank-detail changes never post automatically; they trigger a verification call with the supplier.
- Auto-approval applies only to PO-matched invoices within tolerance and policy limits; everything else has a named approver.
- Duplicates are blocked before posting, not caught at month end.
- Low-confidence extractions are reviewed by a person before matching.
Extraction is solved; matching and routing are the work
Reading fields off an invoice is a solved problem — modern models extract line items from messy PDFs with high accuracy and tell you where they are unsure. The value is in what happens next: matching to the PO and receipt, deciding who has to look at a mismatch and what exactly they are looking at, and coding the non-PO invoices consistently. The workflow spends most of its logic there, and that is where AP time was going.
Fraud controls that a workflow enforces better than people
Invoice fraud usually arrives as a changed bank account on a real supplier's invoice, or a duplicate with a slightly different number. Both are exactly the checks a workflow never forgets: every invoice's bank details are compared to the master, and any change stops the process for a verification call; every invoice is checked for duplicates across supplier, number and amount before posting. Those two rules alone justify the automation for many finance teams.
What to measure
Cycle time from receipt to posting (target: under three days for PO invoices). Touchless rate — invoices posted with no human action — which climbs as coding rules and tolerances are tuned, typically past 60% for PO-heavy businesses. Duplicate and mismatch catches. Early-payment discounts captured, which are pure money the old process was leaving on the table.
What it connects to.
| Tool | Role in this workflow |
|---|---|
| n8n | Capture, validation, routing, posting |
| Claude | Field extraction, non-PO coding, supplier replies |
| NetSuite / Xero / QuickBooks / Sage | ERP of record |
| Slack / email | Approvals |
| Google Drive / S3 | Invoice documents |
Want this running without building it?
$297/month
We set it up in your tools, run it on our servershost it on our n8n cloud (or deploy it to your own n8n, Make or Zapier), watch it, and fix it when something changes. Setup included, cancel monthly; the automation stays yours if you leave.
$5,000–9,000 one-time
Your systems, your rules, your edge cases. A one-off build delivered into your accounts to keepon Claude and n8n, delivered into your accounts to keep, with documentation and a recorded walkthrough.
Covers up to 1,000 invoices a month, one ERP and one AP inbox. Multi-entity, multi-currency approval matrices, or ERPs without an API are a custom build.
Also sold one-time, installed in your own accounts, as part of the accountants package and the accounts payable teams package and the small business owners package — do it yourself $49 · installed for you $249 · done for you $490.
When this becomes a custom build.
The subscription covers the standard version — $297/month, setup and maintenance included. Three things move it to a custom build ($5,000–9,000 one-time), delivered into your accounts to keep. If one of them is you, say so on the audit and the plan prices both.
More than one legal entity or currency, each with its own approval matrix and ledger.
An ERP without a usable API, so posting has to go through a file import or an RPA step.
Purchase-order matching across several systems, or above 1,000 invoices a month.
Running the standard version first is the usual path: the exceptions it logs in the first month are the scope of the custom build, with your own numbers. How custom builds work.
Frequently asked questions.
Which ERPs are supported?
NetSuite, Xero, QuickBooks Online, Sage Intacct, Microsoft Dynamics and SAP Business One via API. ERPs without an API get a validated import file and a manual posting step.
How accurate is the extraction?
Field-level accuracy on typical supplier invoices is high, and every field carries a confidence score; anything below threshold is reviewed by a person before it can be matched or posted. Accuracy improves as supplier-specific layouts are learned.
Does it pay invoices?
No. It posts approved invoices to the ERP; your existing payment run and controls are unchanged.
How accurate is AI invoice extraction?
95–99% of fields on standard invoices, with every field carrying a confidence and the low-confidence ones highlighted for a person — which is the difference between an extraction you can post from and one you cannot. Scans and unusual layouts extract worse on the first invoice and better on the tenth, because corrections feed back.
Does invoice processing automation pay invoices?
No — it posts approved invoices to the ERP with the coding and the trail and schedules them on terms; payment runs stay with finance. Auto-approval applies only to PO-matched invoices within tolerance and a policy limit; bank-detail changes never post without a verification call.
Which ERPs does it support?
NetSuite, Xero, QuickBooks, Sage and SAP directly; others through their import formats. Several entities or currencies with their own approval matrices, an ERP without a usable connection, or matching across systems are custom builds. The accounts payable how-to on this site walks through the whole process step by step.
What this blueprint is built on.
Vendor documentation the steps rely on, and the rules the guardrails are written against.
- Xero — Developer documentation developer.xero.com/documentation/
- Intuit — QuickBooks Online API, getting started developer.intuit.com/app/developer/qbo/docs/get-started
- FBI IC3 — Business email compromise www.ic3.gov/CrimeInfo/BEC