Where the costs of occasional purchases really come from, six levers against administrative overhead — and why process optimization eventually hits its limit.
80% of transactions, 30% of volume: procurement effort concentrates exactly where the least value is created. Occasional purchases hit this point especially hard, because a spare part, a piece of trade-show equipment, or a new office chair costs almost as much to process as a major order.
The reason lies in the process, not in the purchase value. Three steps consume the same amount of time on every order: onboarding the supplier in the system, approval by multiple parties, and the invoice review at the end.
That's as true for €50 as it is for €5,000, because anyone who wants to cut costs doesn't need to push down the purchase price — they need to reduce the number of these cycles.
An example makes this tangible. A department needs a specialist tool for €180, a one-off, and procurement onboards the new supplier, runs a credit check, and approves it before the order passes through two approval levels.
In the end, accounting reviews a €180 invoice almost as thoroughly as an €18,000 one. The process doesn't give small amounts a discount.
These costs don't show up in a single line in the ERP system — they're spread across many parties: procurement, the requesting department, accounting, and IT support for master data maintenance. Because each party only sees its own share, the total effort only becomes visible in aggregate, which is why it stays undetected even though it's real and really does cost time.
The following six approaches reduce the cost per order. Each works at a different point in the same process and has its own limit, which we show at the end of this article. They work best combined, not individually.
Anyone who collects multiple occasional requirements and orders them together spreads the fixed cost of processing across more line items, because a consolidated order needs just one approval instead of five. The effort per item drops noticeably. The comparison of process optimization for one-off requirements shows which approach pays off the most.
Consolidation works well for predictable requirements, such as recurring consumables, but for genuine one-off requirements there's often no time to collect them, because the need is spontaneous and urgent. Anyone who waits until enough has accumulated risks a production stoppage. A broken spare part doesn't wait for the next collection date. A dedicated article covers bundling one-off requirements and C-parts in more depth.
A de minimis threshold simplifies orders below a set value, for example €500: below the threshold, simplified approvals apply, and some companies also use a collective account for this.
Such rules reduce approval effort. Anyone who still has to onboard a new supplier for every new vendor saves on approval, but not on master data maintenance — and for occasional purchases, that's where most of the effort sits. A closer look at processing small orders under €500 correctly shows how that works in practice.
Maverick buying happens when employees order outside the official process, which occurs especially often with occasional purchases, because the official route takes longer than the actual procurement itself.
Policies and approval workflows only address the symptom: they don't change the fact that the official route often remains too slow for a one-off requirement. As long as that's the case, the incentive to bypass it remains. Stricter controls don't solve the underlying problem either — they only make bypassing harder, not unnecessary. A closer look at curbing maverick buying more effectively shows where the real fix has to start.
Every supplier onboarding costs time, because procurement records master data, runs a credit check, and maintains the creditor record — often for a vendor it never orders from again. Why a Simple Order Takes Weeks shows this effect in detail.
One-time creditors or P-cards bypass the full onboarding. But the effort doesn't disappear as a result: it just moves into invoice review or card reconciliation, where someone tallies up the card receipts individually at month-end. It's the same effort, just at a different point. A closer look at ordering without supplier onboarding shows how that's possible in practice.
Anyone who doesn't know their own process costs can't reduce them. The trend is visible industry-wide: procurement teams spend nearly three-quarters of their time on operational processing instead of strategic procurement, on average (Deloitte Global CPO Survey 2021). For occasional purchases, this share is even higher, because every order runs through the same process from scratch.
A simple formula helps quantify this for your own organization: steps involved times time times hourly rate, plus system costs — ten sample orders are already enough for a first reliable figure. That number quickly becomes an argument for change. The in-depth article on measuring process costs per order walks through the methodology in detail.
One-off requirements are spread across hundreds of creditors, collective accounts, and free-text orders, and that's exactly what makes them invisible in reporting, so no one can see at a glance how much these orders really cost.
A creditor analysis or a review of the general ledger accounts creates an initial overview, supplemented with spot checks. But the picture only becomes complete once all one-off requirements run through the same channel — until then, every analysis remains a snapshot, not an ongoing view. A closer look at bringing transparency to one-off requirements shows what a complete picture actually requires.
All six levers optimize the same process. A box of office supplies, ordered spontaneously, still needs its own supplier, its own onboarding, and its own invoice — not even the best approval organization changes that. A closer look at buying irregular office supplies the right way shows what actually solves this.
Hidden Costs in procurement often arise exactly here. In steps that no one prices individually, but that everyone goes through individually, this adds up to a significant number of work hours over a year.
A look at practice shows the limit clearly: a procurement department introduces a de minimis threshold, consolidates predictable requirements, and streamlines approvals, and the effort per order drops noticeably.
Even so, every genuinely new, spontaneous requirement remains at the same starting point: an unknown supplier, a new onboarding, a new invoice, and the levers act on the known part of the process. They change nothing about the unknown part.
This is exactly where process optimization hits its limit. As long as every occasional purchase creates its own creditor, the fixed-cost block per order remains. Consolidation, thresholds, and transparency reduce this block. But they can't eliminate it — that would require the root cause itself to disappear.
The fixed-cost block only disappears once its cause disappears: a new creditor for every occasional purchase. That's exactly what the Single Creditor Model resolves: "One supplier for all one-off requirements."
That's the core idea of the Single Creditor Model: one supplier, one creditor, one consolidated invoice, while agents handle the processing in the background.
No new vendor needs its own creditor anymore. Every occasional purchase instead runs through a single, already existing supplier relationship. No more one-time creditors (one creditor for all one-off requirements, no more supplier onboarding). The spare part, the trade-show equipment, the office chair: all run through the same channel.
The effect touches all three cost blocks at once. Onboarding is eliminated because no new creditor is needed, and approval shortens because the review effort for a known vendor is lower.
And the invoice arrives consolidated, instead of accounting reviewing it individually for every micro-order. The six levers from above remain useful here, because they now no longer work against a growing pile of individual cases, but within a single, stable process.
More on the mechanism behind it: The Single Creditor Model.
Find out how the Single Creditor Model structurally reduces your administrative costs for occasional purchases: Schedule a call →
