A lot of accounts payable advice is built around three-way matching. The purchase order says what was ordered, the goods receipt says what arrived, and the invoice says what the supplier wants paid. If the three agree, the bill goes through.
That works well for companies with a procurement team. It describes very few small businesses. In a 30-person company, the office manager orders printer toner on a call, the operations lead agrees a monthly price with a cleaning contractor over WhatsApp, and the owner signs a software subscription with a card. Nobody raises a PO for any of it, and nobody should have to. Forcing a formal purchasing process onto that kind of spending usually just means people raise the PO after the invoice arrives, which adds a step and checks nothing.
So the useful question for an SME is how to approve bills properly when there’s nothing to match them against. The answer is a set of simple rules about who looks at what, and what they are actually checking when they do.
What a PO does, and what replaces it
It helps to be specific about what a purchase order gives you, because each part needs a substitute.
A PO proves that someone with authority agreed to the spend before it happened. It fixes the price and quantity in advance. It tells AP who the internal owner is. And it gives the system something to compare the invoice against automatically.
Without a PO, the approval step has to do all four jobs after the fact. The approver confirms the spend was wanted, checks the amount against what was agreed, takes ownership of the cost, and catches anything odd. That is a lot to ask of someone who opens a notification on their phone between meetings and taps “approve”. Most weak non-PO processes fail right there: approval becomes a formality, and nobody is really checking anything.
Sort your bills before you design approvals
Non-PO invoices are not one category. A practical split for most SMEs has three groups.
The first is recurring, contract-based spend: rent, utilities, internet, insurance, software subscriptions, retained services like an accountant or a cleaning company. The supplier and the rough amount are known in advance. These are the bills where you want the least human effort, because the risk is mostly in the amount changing or the bank details changing, both of which can be checked mechanically.
The second is regular operational spend from known suppliers with variable amounts: raw materials, courier fees, freelance work billed by the hour, maintenance call-outs. The supplier is familiar but the amount needs someone who knows what was delivered to confirm it.
The third is one-off or new-supplier spend. A first invoice from a company you have never paid before, an unusual purchase, an invoice that turned up without anyone expecting it. This is where both errors and fraud tend to concentrate, and it deserves the closest look.
Once bills are grouped this way, the approval rules almost write themselves.
Approval rules that work at small-team scale
For recurring contract spend, the cleanest setup is to approve the contract once and then let invoices within a tolerance go through on a light check. If the internet bill is normally within a few percent of the same amount, there is no reason for the owner to look at it every month. What should stop it is a change in amount beyond your tolerance, a change in bank details, or a duplicate invoice number. Those are rules, and they can be enforced without a person reading every bill.
For variable spend from known suppliers, route the bill to the person who received the goods or managed the work. This is the closest thing to a goods receipt that a small business has. The warehouse lead confirms the delivery happened, the project manager confirms the freelancer’s hours. Finance then checks coding and tax, but finance should not be the one confirming that work was done, because they usually have no way of knowing.
For new suppliers and one-offs, require a second set of eyes and a check of the supplier itself before the bill is approved. Is this a real company? Do the tax registration number and address match what they say? Did someone in the business actually engage them? Confirm bank details through a contact you already had, not one printed on the invoice.
Amount thresholds sit on top of these groups. A common pattern is that anything below a small limit only needs the budget owner, anything above it also needs a manager or the owner, and anything above a higher limit needs the owner regardless of category. The specific numbers depend on your size. The point is that the limits are written down and applied the same way every time, so approvals don’t depend on who happens to be in the office.
The checks an approver should actually make
Approvers tend to approve. Give them a short, concrete list instead of a vague responsibility to “review”.
Did we order this, and from this supplier? Does the amount match what was agreed, or what was delivered? Is it coded to the right cost center or account, or at least to the right budget owner? Have we seen this invoice before, possibly under a slightly different number or sent through a different channel? Have the supplier’s bank details changed since the last payment?
The last two are where the expensive mistakes come from, and they are also the ones a person is worst at spotting. A human approver will not remember that the same invoice arrived as a PDF by email three weeks ago and as a photo on WhatsApp yesterday. They will not notice that one digit in an IBAN is different. Those checks belong in the system, so the approver can spend their attention on whether the spend makes sense. We have covered both in more detail in our posts on duplicate invoice payments and bank detail warning signs.
Where non-PO approvals slow down
The common complaint about approval workflows is speed rather than control. Bills sit in someone’s inbox for a week, the supplier chases, and someone in finance ends up approving it themselves to make the problem go away.
This shows up clearly in benchmark data. Ardent Partners’ State of ePayables 2025 report puts invoice processing time at 13.5 days for AP teams outside its Best-in-Class group, against 2.9 days for the Best-in-Class teams. Exception rates follow a similar pattern, 20.9% of invoices for everyone else against 11.1% for the Best-in-Class group. A large part of that gap is invoices waiting for a person: an approver who hasn’t responded, or an exception nobody owns.
A few habits help a lot here. Make sure every bill has exactly one named approver when it arrives, instead of a group or a shared inbox. Send approval requests where people already are, which for many SMEs means a phone, not a desktop login they use once a month. Set a reminder after a day or two and a fallback approver after a few more. And keep the information the approver needs on the request itself: the invoice image, the supplier’s history, the amount compared with last time. If the approver has to open three systems to make a decision, they will put it off.
Faster approvals also give you choices on payment timing. If bills are approved within days instead of weeks, you can decide to pay on the due date, or early when a supplier offers a discount, instead of paying whenever the approval finally comes through. The payment terms calculator is a quick way to see what a given set of terms is worth.
Keeping the record in your accounting system
One more thing that matters more without POs: the approval record. With a PO, the authorization lives in the purchasing document. Without one, the only evidence that the spend was authorized is the approval itself. If that approval happened in a WhatsApp chat or a verbal “yes, pay it”, there’s nothing for an auditor or your future self to check.
Whatever tool you use, the approved bill in your accounting system should carry who approved it, when, and what they saw. Many accounting systems such as Xero, QuickBooks and Zoho Books offer some form of bill approval or user permissions, and those are worth switching on even if you add nothing else, though the depth of approval routing varies a lot by product and plan.
Where a tool like Clearline fits
There are two broad ways to automate this. Full procure-to-pay platforms give you requisitions, POs and approval workflows in one place, and they make sense if you want to introduce purchasing discipline and are willing to move your process onto a new system. If your business runs on informal buying and you want to keep it that way, a layer on top of your existing accounting system is usually a better match.
Clearline is built for the second case. It reads invoices from WhatsApp, email or upload without templates, checks each one against what that supplier has billed before for duplicates and against the bank details used last time, sends only the uncertain fields to a person, and posts the approved bill into the accounting system you already use with a full history of who approved what. There is no purchasing module to adopt and no change to how your team buys things.
If your bills mostly arrive without a PO, start with the three groups above, write down your thresholds, and make sure the checks that people are bad at are done by something that doesn’t get tired. That covers most of what a PO would have given you.