Purchase order software: getting approvals out of email

What purchase order software actually needs to do

Strip away the vendor marketing and a purchase order system has a short list of real jobs: capture a request with enough detail to approve it, route it to the correct approver based on value or category, keep a record of who approved what and when, generate the order itself, and match it against the invoice when the goods or service arrive. Everything else is a feature layered on top of that core.

Why email and spreadsheets stop working

Email approval works fine when a business has one or two people who can say yes. It breaks down the moment there's more than one approval tier, more than one department with its own budget, or more than a handful of requests a week. At that point nobody has a reliable view of what's pending, what's been approved, or what's already been spent against a budget this quarter.

Spreadsheets fare a little better because they at least centralise the record, but they don't stop someone bypassing the process entirely, and they don't notify an approver that something is waiting on them. A spreadsheet is a record, not a workflow - it tells you what happened, not what needs to happen next.

• No automatic routing: every request depends on someone remembering who needs to sign it off.
• No enforced limits: a £50 request and a £5,000 request go through the same inbox with the same visibility.
• No audit trail: reconstructing an approval decision means searching sent items and hoping nothing was deleted.
• No link to budget: approvers say yes without seeing what's already been committed against the same cost centre.

Off-the-shelf vs building it into your existing systems

There are good standalone purchase order tools on the market, and for a business with a fairly standard buying process and no existing finance or ERP system worth integrating with, one of those is often the fastest route. The trade-off is that you're adopting someone else's approval logic and living with its limits on customisation.

Where it usually makes more sense to build the workflow into what you already have - inside your ERP system or as a lightweight business process automation layer - is when your approval rules are genuinely specific: different limits by department, project-based budgets, multi-currency suppliers, or a requirement to match against a live budget rather than a static limit. Bolting a generic PO tool onto that setup often creates a second source of truth rather than removing one.

A hybrid is common in practice: a standard finance system handles the accounting and payment side, with a purpose-built requisition and approval front end that matches how your teams actually request things, feeding orders into the finance system rather than duplicating it.

Getting the approval rules right before anything is built

The most common reason a new purchase order system gets ignored within a few months is that the approval rules don't match reality. If a manager routinely needs to approve something urgently from their phone and the system only works at a desk, they'll go back to email. If the value thresholds don't reflect how the business actually delegates spend, people will find workarounds.

Before choosing or building anything, map the actual rules: who can request what, what limits apply at each level, what happens when an approver is away, and which categories of spend (capital, recurring subscriptions, one-off project costs) need different treatment. This is exactly the kind of thing business process mapping is for, and skipping it is the single biggest reason PO systems get rejected by the people meant to use them.

Integration with the systems you already run

A purchase order sitting on its own, disconnected from accounts payable, stock, or your project costing, only solves half the problem. The value multiplies when an approved PO automatically updates a budget, triggers a goods-in check, or matches against an invoice without someone re-keying figures. Check early whether a candidate tool has a genuine API integration with your accounting package or ERP, rather than a CSV export you'll be running manually every week.

What to check before you commit

1. 01Can approval rules be set by value, department and category, not just a single flat limit?
2. 02Does it work properly on mobile, since delayed approvals are usually the whole problem you're solving?
3. 03Can it integrate with your accounting or ERP system, or will you be exporting data manually?
4. 04Is there a full audit trail that would satisfy an external audit, not just an internal report?
5. 05What happens to a request when the named approver is on leave or leaves the business?
6. 06Can you configure it yourself as rules change, or does every tweak require a support ticket?

If your approval process is unusual enough that no off-the-shelf tool fits it comfortably, get in touch and we'll talk through whether a bespoke workflow, or a lighter integration into what you already run, is the better route for your business.