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In a company of forty people, a purchase often takes the shortest path: the workshop manager calls the supplier, marketing orders with the company card, the IT manager takes out an online subscription. Each purchase is reasonable. Their total is discovered on the invoice, or in the annual accounts, and nobody knows any more who approved what.
The remedy is not a heavy procedure. It is a single entry point and a few approval rules, which an n8n workflow applies without wasting the requesters’ time. This article is part of the n8n workflows: what each department can automate series, purchasing section.
In short
A single entry point for all requests: a short form.
The approver depends on the amount and the department, following written thresholds.
The department’s remaining budget is shown at the moment of approval.
Approval creates the purchase order and informs the requester.
Small recurring purchases go through without approval, within a set limit.
What the lack of a circuit costs
The cost is not only the unnecessary purchase. It is the duplicate purchase, because two departments ordered the same thing. It is the subscription that carries on after the person who took it out has left. It is the invoice that reaches accounting with no purchase order, which the accountant has to get approved after the fact, chasing signatures.
A purchase request circuit solves these three points at once, because it makes the purchase exist before the invoice.
The path of a request
A purchase request in n8n
- The request
The requester describes the need, the estimated amount and the intended supplier.
- The approval
The workflow sends it to the planned approver, with the remaining budget.
- The order
Once approved, the purchase order is created and sent.
- The tracking
Delivery and invoice are linked to the original request.
The form fits on one page. The n8n form trigger is enough, or a form in the internal tool already in use. What matters is that there is only one door, and that it is quicker than calling the supplier directly. Otherwise, requesters will go around it.
Approval thresholds
- Below a small amount.
No approval, just a record, for routine purchases from a list of usual suppliers.
- Medium amount.
The head of the department approves.
- High amount.
The head of the department, then the finance director.
- Long commitment.
Any subscription or contract of more than a year goes to management, whatever its monthly amount.
The exact thresholds are a management decision, not a tool decision. They are set according to the size of the company and the trust given to departments. The fourth level deserves a mention: a modest monthly subscription can commit the company for several years, and that is where many forgotten costs hide.
With or without an ERP
If the company has an ERP with a purchasing module, the approval circuit often already happens there, from request to supplier payment: the article Purchasing in an ERP describes the steps. The n8n workflow then keeps a narrower role: capturing requests that come from elsewhere (email, a simple form for those without an ERP account) and creating them in it.
Without an ERP, the workflow carries the whole circuit: a table of requests, the approvals, the purchase order generated from a template, and linking the invoice when it arrives. That last point connects with automated reading of supplier invoices, which can find the original request by its number.
What the requester gains
The purchasing circuit is often presented as a constraint for departments. Done well, it is the opposite. The requester knows where their request stands, without chasing. They no longer have to find out who needs to sign. And when the order is late, delivery tracking takes over: the workflow that spots late suppliers starts from the date promised on the purchase order.
To set up this circuit with your thresholds and your tools, our n8n automation offer starts from your actual purchases over recent months and the cases that caused problems.
Frequently asked questions
Will the circuit slow down urgent purchases?
It can include an urgent route: the request goes to the approver with a clear label, and the approver gets an immediate notification on their phone. The urgent purchase stays on record, without waiting. What really slows purchases down is the lack of a circuit, when the requester does not know who should approve and waits for an answer that never comes.
How do you handle software subscriptions taken out online?
They go through the same form, with a “subscription” type that asks for the commitment period and the person responsible. The workflow can then remind that person of each renewal date, and they confirm whether to keep the tool. It is the simplest way to avoid subscriptions that carry on after the people who used them have left.
Should you track a budget per department?
It is useful as soon as there is an annual budget per department. The workflow shows the approver what is left, calculated from requests already approved. It does not block anything: the approver can go over, knowingly. Without a defined budget, start by tracking spending per department for a few months, then set one.
Sources
- Form, n8n documentation (new tab)docs.n8n.io
Jim · founder of Brain Plus AI
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