Invoice approval workflow: How to automate invoice approvals

Your invoice approval workflow stalls the moment an invoice reaches a cost center owner who never opens the ERP. AP chases by email. The approver answers days later from a phone while the payment terms keep running.

According to Ardent Partners (2025), the average invoice takes 8.2 days to process. Every day an invoice waits for a signature is a day closer to a missed early payment discount.

This guide follows the invoice approval process from receipt to posting. It then shows how to build an approval matrix that fits your organization and how to keep every decision audit-ready.

Key takeaways

• Code before you route: the general ledger account and cost center on an invoice decide who approves it
• An approval matrix ties each amount band and cost center to a named approver and a deputy
• Approvers without ERP access can decide from a web or mobile inbox, or straight from an email with no login
• A four-eyes check and a full audit trail show auditors that the required number of different people approved each invoice
• Finance can keep reviewer and approver lists current in an administration console without writing code

What is an invoice approval workflow?

An invoice approval workflow is the sequence of checks and sign-offs a supplier invoice passes before your company pays it. It confirms that the invoice matches what you ordered and received and that a person with the authority to release the payment has approved it. Every step leaves a record you can show an auditor.

The invoice approval process, step by step

Hey, Doxi! How do I automate my invoice approval workflow?

Build an approval matrix that fits your organization

An approval matrix is the rulebook behind the routing: it says who approves which invoice and who steps in when they are away. Write it down before you automate anything, because software can only enforce rules that exist.

Set thresholds by amount and cost center

Pair each amount band with a role. The bands below are an illustration, so replace them with the limits from your own signing authority policy.

Add one rule on top of the bands: the owner of the cost center on the invoice always signs first, whatever the amount. Keep the number of levels small. Every extra level adds a wait, so add one only where the amount or the risk justifies it.

Decide who signs off at each level

Assign each level to a role, such as the budget owner for a cost center. A role survives a reorganization, and the matrix needs only a list update when someone changes jobs.

Plan for absences and deputies

Give every approver a named deputy for vacation and sick leave, or invoices wait until the approver returns. Set a limit for the deputy as well, because a deputy who can approve any amount is a control gap. Make sure a deputy never approves an invoice they requested themselves.

Decide what happens to exceptions and rejections

Define the path before the first exception arrives. A rejected invoice goes back to AP with the reason. AP asks the supplier for a corrected invoice, and the approval starts again at the first level. According to Ardent Partners (2025), the average AP department sees exceptions on 18.4% of its invoices, so this path gets used every day.

Get every approver into the workflow, even without ERP access

Most approvers are budget owners in the business units, and they should not need a license for your ERP (SAP or Oracle, for example) to approve an invoice. If approval requires a login they rarely use, invoices wait and AP ends up chasing by email.

With Doxis, approvers work from a web or mobile inbox that shows the invoices waiting for them. They can also decide straight from an email that lists the invoice line items: one click approves or rejects, and a reply to that email adds the reason. The decision is written back into the process and the approver never logs in.

Send approvers a sample of that email before go-live, so the first real one does not look like phishing.

Prove who approved what

Auditors testing internal controls under SOX ask for the same proof every time: who approved each invoice, and whether enough different people were involved.

Doxis checks the four-eyes principle for you. Before an invoice can be posted, it verifies that the required number of different reviewers and approvers has acted. Every action lands in the audit trail and the document history, and your auditor gets the trail as a CSV export.

Check four things before the first invoice goes through:

• The required number of approvers is set for each amount band
• Audit logging is switched on for every document category you approve
• Each deputy has a limit of their own
• One named person reviews the approver lists every quarter

Keep the approval rules in finance's hands

Approval rules change with every reorganization and every new signing limit, and each change should reach the workflow quickly.

With Doxis, a business administrator maintains the lists of reviewers and approvers in the web administration console. No code is needed, so adding an approver takes no IT ticket. The same console sets the rule for how invoice header and line item amounts are checked.

Invoices with several cost centers get item-level release. Each invoice line goes to the approver who owns that cost center, and you decide whether the header and line amounts must all match or one is enough.

How invoice approval works in SAP

If your ERP is SAP, the same approval matrix maps onto the approval workflow in Doxis P2P for SAP. Approvers can decide inside SAP or outside it, and every step is documented.

Route by amount and cost center

Approval routing follows your amount and cost center rules through multi-level approval chains. An invoice goes to the cost center owner first and moves through the approval levels you define as the amount grows, so the matrix from the previous section maps directly onto the workflow.

Keep invoices moving with deputies and escalations

Deputy rules cover absences. Reminders and escalations chase overdue approvals, so AP does not have to.

Let colleagues without SAP access approve

Not every approver has an SAP login, and they do not need one. The approval app that is part of the same platform runs in a browser or on a phone, so they review the invoice and decide there. The decision stays part of the same workflow.

Eissmann halves invoice processing time with Doxis

Eissmann Group Automotive supplies vehicle interiors with 5,000 employees across 12 locations. Its invoices were processed manually in separate systems, and the rollout had to work across two ERP systems and several languages.

The company automated inbound invoice processing from capture through workflow-supported verification to audit-proof retention. Employees release invoices through a web application, and an access rights concept lets each person see and approve only the invoices they are responsible for. Up to 3,800 employees can take part in the workflow.

• Average processing time per invoice fell from 15 to 17 minutes to 5 to 8 minutes
• Daily volume grew from about 80 invoices to 100 to 120, handled by the same team
• Every processing step is logged for audits

At far larger volume, Eli Lilly, a US pharmaceutical company with 50,000 employees, processes more than 600,000 invoices a year across nearly 100 countries with Doxis, built into its SAP workflow.

Get invoice approvals under control with Doxis

Invoice approvals stall where the process meets people who work outside the finance system. Doxis brings those approvers into the workflow and records each decision, so every invoice leaves the same evidence behind.

Invoice approval is one process on a platform built to run many. Doxis AI.dp reads the invoice data on arrival, the approval workflow routes it, and audit-proof archiving keeps the invoice with its approval history. The same platform covers approvals in purchase-to-pay and contract management, so the next process can run on the platform you already have.

According to a Forrester Consulting study, SEW-EURODRIVE achieved a 336% ROI over three years, with payback in under six months, running document management and process automation on one platform.

• Approvers decide from a web or mobile inbox, or from an email with no login
• A four-eyes check confirms the required number of different people approved before posting
• Every action is logged, and the history exports as a CSV file for your auditor
• Deputy rules keep invoices moving when an approver is away
• Capture, approval and archiving run in one workflow, so each invoice keeps its full history
• The same platform extends to purchase requests and contracts when you are ready

Doxis is a Leader in the Gartner® Magic Quadrant™ for Document Management 2026.

Request a free demo below and see how your approval matrix would run, from capture to archive.