Document Workflow and Invoice Approval from KSeF: How to Design It Properly

A well-designed invoice approval workflow from KSeF answers three questions before an invoice ever reaches the accountant: who reviews it, within what timeframe, and what happens if nobody responds. Without answers to these three, even the best KSeF API integration ends up exactly where things stand today: an invoice sitting in an inbox, waiting for someone to notice it.

I've already covered pulling invoices from KSeF in a separate piece on automatic download of purchase invoices — that one focused on the technical side. Here I'm setting the API aside and dealing with what happens to an invoice from the moment it lands in the system until the bookkeeper actually posts it. The full scope of that service, from download to approval workflow, is on the KSeF automation and invoice workflow page. This stage is where most KSeF rollouts go wrong, because companies prepare for the technical part and forget that an approval workflow is an organisational process, not an IT one.

Written in October 2026, based on my own implementations. I cover KSeF deadlines and regulations more broadly in the KSeF 2026 guide — this piece assumes the obligation already applies to you, or is about to.

Why "someone clicks approve" isn't enough

The simplest workflow I've seen looks like this: an invoice arrives at one shared mailbox, someone looks at it and replies "fine". That works as long as one person in the company handles costs. The moment there's a second department, a second site, or the first invoice above a certain amount, this model falls apart, because it has no answer to any of the following:

• What happens if the person who approves is on holiday?
• Who decides when an invoice touches two departments at once?
• Does a £45 invoice for printer paper need the same path as a £9,000 invoice for a machine?
• What happens if nobody responds within a week?

Designing a workflow starts with writing down answers to these questions, not with picking a tool. Only after that do I choose between n8n, Make, or a document-workflow module already built into the accounting software.

Three approval-path patterns

In practice I most often combine the second and third pattern: the invoice first goes to whoever owns the cost category, and only above a set amount does it also go to the board. That gives control without drowning management in dozens of small invoices.

Step by step: what a properly designed workflow looks like

1. Categorisation. After the XML is read from KSeF, the automation checks the supplier's tax number and suggests a cost category based on past invoices from that supplier. The first few invoices from a new supplier need manual tagging; after that, the system learns.
2. Path selection. Based on category and amount, the system decides who must approve the invoice — one person, two people in sequence, or a category owner plus the board above a threshold.
3. Notification. The approver gets a message (email, Teams, Slack) with a PDF preview, amount, supplier, and one button for the decision — approve or reject with a comment.
4. Reminder. If nobody reacts within an agreed window (usually 2–3 working days), the automation sends a reminder, and after a further deadline it escalates to that person's manager.
5. Decision log. Who approved it, when, and with what comment — all of it stays on record. In an audit, or a dispute with a supplier, that history is worth more than the invoice itself.
6. Handover to accounting. The approved invoice reaches the accounting software with its category noted, so the bookkeeper can post it without chasing the team for answers.

The same structure can be built in n8n with Teams notifications, in Make with a spreadsheet integration, or in a ready-made document-workflow module if the accounting software already has one. The choice of tool depends on how many people take part in approvals and whether the company already has other automations the workflow should plug into.

What about invoices with no clear owner

This question comes up in almost every rollout: a supplier nobody recognises, or an invoice two departments keep forwarding back to each other. A good workflow doesn't solve this automatically — and shouldn't try to. Instead:

• I set a default "owner of unassigned invoices" (usually admin staff or purchasing),
• such an invoice gets a shorter response window than normal (1 day, not 3),
• once assigned to a department, the system remembers the rule for future invoices from the same supplier.

From what I've seen across implementations, the number of these "orphan" invoices drops sharply after the first month, because the system learns the assignments and the team simply starts knowing what to expect.

Three observations from implementations

First: most of the time goes into talking through exceptions, not building the technical bits. Sentences like "fleet manager approves fuel, but only up to £450, above that it goes to the CEO, unless it's a fuel-card station" need to be written down and tested against real invoices from recent months before the workflow goes live.

Second: reminders need a ceiling, or they turn into noise. At one company I set reminders every 24 hours with no upper limit, and within a week people started ignoring them like spam. A sensible rule is 2–3 reminders, then escalation to a manager — not another ping to the same person.

Third: workflows break because of staff changes, not KSeF changes. Someone who used to approve transport invoices leaving the company, with nobody updating the rule, causes more disruption than a change in the Ministry of Finance's API. A quarterly review of approval rules takes 15 minutes and saves weeks of confusion.

An example scenario

An illustrative scenario, not a specific client. A manufacturing company with 25 staff, three departments (production, logistics, admin), roughly 150 cost invoices a month. Before the rollout, every invoice went by email to the bookkeeper, who informally decided who to ask for approval — effectively doing a job she was never trained for and wasn't accountable for.

After the rollout, the invoice automatically goes to the relevant department head based on cost category, and anything above £1,100 also goes to the board. The bookkeeper receives an already-approved invoice with its category noted. Time the bookkeeper spends "chasing who's supposed to approve this" drops from several hours a week to practically zero, and the finance director has a full decision history on hand for any audit. Rough costs for this level of rollout (the "cost invoice automation" tier) are in the KSeF implementation cost article — typically £650–£1,750 one-off plus £35–£110 a month to maintain.

Common mistakes when designing a workflow

• Too many approval layers from day one. Three people having to sign off on every invoice, including the one for office coffee. I start with a simple scheme and add layers only where there's real risk.
• No cover for holidays. One approver, zero backup — invoices sit for two weeks because nobody wants to "step into someone else's lane".
• A path built around the current team, not the process. A rule like "Anna approves it" instead of "the logistics manager approves it" falls apart the day Anna changes departments.
• No decision history at all. A verbal "fine, approved" over the phone never gets recorded, and later nobody remembers whether the invoice was actually checked.
• Treating the workflow as a one-off project. The company grows, suppliers change, and the rules from launch day sit untouched for two years.

How to tell if the workflow is actually working

A workflow can't be judged on whether it "sort of" works. After a month or two in production, it's worth checking a few concrete numbers:

• Average time from invoice download to approval. If it creeps up week on week, there's a bottleneck somewhere in the path — often one person overloaded with approvals across several categories at once.
• Number of invoices reminded more than once. That's a sign the person either doesn't have the time, or shouldn't be the sole approver for that category.
• Number of "orphan" invoices with no assigned owner. This should fall month on month. If it stays flat, the categorisation rules need tightening.
• Number of rejections and their reasons. Rejections aren't a problem — they're information. A recurring reason (say, "no purchase order on file") points to the purchasing process, not the approval workflow itself, needing a fix.

I collect these four numbers automatically in the same system that handles approvals, and review them with the client quarterly alongside the rule review mentioned above. That catches a problem before it turns into a pile of invoices waiting at month-end.

FAQ

Does an invoice approval workflow have to be integrated with KSeF?

It doesn't have to be, but it's worth it: a KSeF invoice is structured data (XML), so the automation can pull the amount, supplier and number straight away and route it down the right path — without retyping anything.

Which tool is best for building a workflow?

It depends on headcount and existing systems. A simple workflow is covered by a module in the accounting software. For more complex rules (categories, amount thresholds, escalations), n8n or Make connected to Teams or Slack tends to work well.

What if two departments argue over who should approve an invoice?

Set a default owner for unassigned invoices with a shorter response window, and resolve disputed cases once, recording the rule for that supplier going forward.

Can a small approval workflow be expanded later?

Yes, and that's usually what I'd recommend. A simple single-approver workflow can be expanded with categories and amount thresholds once invoice volume or headcount grows.

How long does it take to set up an approval workflow?

For a company that already pulls invoices from KSeF, designing and rolling out the approval workflow itself usually takes 1–2 weeks — most of that time goes into discussing rules and exceptions, not configuration.

Summary

The invoice approval workflow is where KSeF automation actually pays off — not at the stage of pulling the XML, but at the stage of deciding who approves a cost and when. Start by writing down the exceptions you currently resolve over the phone, because those, not the technology, decide whether the workflow still works six months from now.

If you want to design an invoice approval workflow for your business, get in touch through the contact form. A first conversation about how your current process works is free.