A wage cost increase in a service contract runs through the indexation clause. A supplier may pass on higher wage costs, but only according to the method laid down in the contract: which index, which reference date, which weighting. If the invoiced percentage does not match that agreement, you pay too much. With a portfolio of dozens of contracts, that difference almost never gets noticed.
As of 1 July 2026, the statutory minimum wage has been raised again. For labour-intensive outsourced services such as cleaning, security and catering, that means a few percent in extra wage costs. This increase does not arrive with a separate letter. It sits hidden in an indexation line on your invoice, somewhere in July or August. In facility services, wages are the dominant cost item. A minimum wage jump therefore feeds straight through into the price you pay. The problem rarely lies with the supplier. It lies with the lack of overview on the client side.
Which outsourced contracts does a wage cost increase affect?
A wage cost increase through indexation affects every service contract where labour is the largest cost item. Think of cleaning, security, catering, reception services and grounds maintenance. In these contracts, 60 to 80 percent of the price consists of wages. An increase in the minimum wage therefore feeds through almost entirely into the rate.
The increase comes in through the indexation clause in the contract. This often happens automatically. The supplier sends an adjusted invoice with an indexation percentage, and it gets paid. With a single contract, that is manageable. For an organisation with 40 to 200 active contracts, it becomes an impossible task. After all, every supplier has its own indexation arrangement, and no one checks per invoice whether it is correct.
Why isn’t an indexation line on your invoice automatically correct?
An indexation percentage on an invoice means nothing on its own. It is only correct if it matches the method you laid down in the contract. And that is where things often go wrong, not out of bad intent but through fragmentation. There are four points to check before you pay an indexed invoice.
- The index used. Does the contract index on the consumer price index (CPI) or on the collective labour agreement wage index? A contract that indexes on CPI alone does not capture a wage cost increase cleanly. General inflation does not move in step with actual wage growth.
- The reference date. Which month or which quarter is the reference point? The wrong reference date quickly produces a deviating percentage.
- Provisional or final figure. Statistics offices such as CBS first publish provisional figures, then final ones later. A supplier working with a provisional figure may end up higher than the agreement allows.
- The weighting. Many service contracts use differentiated indexation, for example 70 percent labour and 30 percent materials. If the weighting is wrong, the outcome is wrong.
Watch out for a common mistake too: indexation must not depend on whether a supplier meets its KPIs. Price indexation and performance are two separate mechanisms. Mixing them up leads to disputes at the negotiating table.
Worked example: is that 4 percent indexation actually correct?
Take a cleaning contract with differentiated indexation: 70 percent labour, 30 percent materials. The collective agreement wage index rises by 5 percent, the materials component (CPI) by 2 percent. You calculate the correct indexation like this:
- Labour share: 70% x 5% = 3.5%
- Materials share: 30% x 2% = 0.6%
- Total: 3.5% + 0.6% = 4.1%
Suppose the supplier applies 5 percent on the invoice. On a contract of 200,000 euros a year, that difference of 0.9 percentage points amounts to around 1,800 euros. On a single contract, that seems manageable. Across a portfolio of dozens of contracts, the amount adds up fast. Half a to a full percentage point too much each time, and no one notices because there is no overall overview. An organisation aiming to save 8 percent a year on contract costs quietly gives that loss straight back.
The real problem: you can’t see the accumulation
The core of a wage cost increase in service contracts through indexation is not one incorrect invoice. It is the sum total. In an FM organisation with contracts spread across multiple sites and suppliers, different indexation arrangements, different reference dates and different weightings all apply. The indexation clauses sit in PDFs, in folder structures, in the heads of people who have sometimes already left.
The result: a contract manager holding an invoice in August cannot quickly establish what the agreed method was. So the indexation is simply accepted. A small deviation per contract, times dozens of contracts, times several years. That is how budget disappears without anyone being able to point to a mistake. The solution does not start with negotiating clauses more strictly, but with making the agreements you already have testable.
How to check indexation in your financial administration
You get a grip by recording the indexation arrangement in the place where you need it: linked to the contract, not in a separate document. In the GRIP Contract Dashboard you record per contract which index applies, which reference date, which weighting and which figure (provisional or final) you apply. When the invoice comes in, you test the invoiced percentage against that arrangement instead of accepting it.
The overview beforehand matters just as much. In a single dashboard you can see which contracts may apply an indexation from 1 July and what the expected impact is. That way you know what the minimum wage increase means for your annual budget before the invoices arrive. You can then substantiate that towards procurement or the board without loose calculations in Excel. For organisations in healthcare facing budget pressure and many labour-intensive contracts, that is the difference between steering and reacting after the fact.
Frequently asked questions about wage cost increases and indexation
Can a supplier always pass on a wage cost increase?
Only if the contract has an indexation clause that allows it. The supplier may pass on costs according to the method laid down: the agreed index, reference date and weighting. Without a clear clause, or where the percentage deviates, you have grounds to dispute the invoice.
What is the difference between CPI and the collective agreement wage index in indexation?
The CPI (consumer price index) measures general inflation. The collective agreement wage index measures the actual increase in wage costs in a sector. For labour-intensive services, the collective agreement wage index fits better, because wages make up 60 to 80 percent of the price. A contract that indexes on CPI alone does not capture a wage cost increase cleanly.
How do I calculate differentiated indexation?
You multiply each part of the contract by the corresponding index increase and add the results together. With 70 percent labour (5 percent increase) and 30 percent materials (2 percent increase), the correct indexation is 3.5 plus 0.6, which is 4.1 percent. If the weighting on the invoice is wrong, the percentage is wrong too.
Can indexation be tied to meeting KPIs?
No. Price indexation and performance are two separate mechanisms. Indexation compensates for higher costs, KPI agreements steer on quality. Mixing them up leads to unnecessary disputes and an unclear contract.
Why does the wrong reference date cost money?
The reference date determines which index figure you apply. A shift of a month or a quarter can already change the percentage measurably. Always test the reference date on the invoice against the date stated in the contract.
How do I prevent small indexation errors from accumulating?
Record the indexation arrangement centrally per contract and test every indexed invoice against that arrangement. That way you see deviations per contract and the sum total across your whole portfolio. With dozens of contracts, that is the only point where you can still see the accumulation.
Want to see how to make indexation testable per contract against your invoices? See how organisations tackle this with GRIP or book a demo.