It’s October. The controller asks what the cleaning contract will cost next year. You grab the latest invoice, add a percentage and email the figure across. In March it turns out the cleaning collective labour agreement rose more sharply than you thought, and there’s still thirty thousand euros of additional work outstanding that was never booked. Now you get to explain why you’re over budget. Justifying your contract budget means preventing exactly that: knowing what your figure is based on, instead of gambling on last year plus three per cent.
The short answer: your forecast only holds up when you build it from the actual contract terms. Indexation per component, collective labour agreement increases, outstanding additional work and volume changes all feed through differently. That data already sits in your checked invoices. The trouble is that it usually lives scattered across separate PDFs and Excel tabs that no one can reproduce.
Why invoice value plus a percentage doesn’t work
Most organisations budget like this: take last year’s invoice value, add a general indexation percentage, done. It feels safe, but you start your forecast on the wrong footing. The CBS consumer price index stood at 3.3 per cent for 2024 (CBS, figure checked October 2025). The problem is that this percentage tells you nothing about a cleaning contract, where labour costs make up the largest share.
A labour-intensive contract moves with the collective labour agreement, not with the weekly shop. Budget with the general index anyway, and you’re likely to forecast structurally too low. Four items trip up an invoice-value-plus-X forecast most often:
- Indexation, and the question of which index exactly, and on which part of the amount
- Collective labour agreement wage increases that are separate from the general price index
- Outstanding additional work you agreed this year but haven’t yet invoiced
- Volume changes: extra square metres, a new location, more users
Contract value is not the same as contract budget
This distinction is the one most often confused. The contract value is the figure stated in the contract: the agreed price for the agreed scope. The contract budget is what you will actually spend in a financial year. The two almost always diverge.
A contract that starts in June only counts for seven months in its first year. Additional work falls outside the original value but does appear in your spend. And an indexation that takes effect on 1 January raises your budget while the contract value on paper stays the same. Budget on the contract value and you’re working with the wrong number. The budget is the sum of what will actually run.
A worked example: where the difference sits
Take a cleaning contract with an invoice value of 400,000 euros over the past year. The lazy method: 400,000 plus 3 per cent general indexation becomes 412,000 euros. That’s what you budget with.
Now the substantiated version. Labour costs make up 80 per cent of the contract, or 320,000 euros, and index with the cleaning collective labour agreement, which comes to 4.5 per cent. That’s 14,400 euros extra. The materials component of 80,000 euros indexes at 2 per cent, which is 1,600 euros. On top of that, 18,000 euros of additional work from this year remains outstanding and will be invoiced next year, and you’re opening a second location that raises volume by 6 per cent. Added together, you land well above 450,000 euros.
The gap with your lazy forecast of 412,000 euros runs towards 40,000 euros. That’s not a rounding error. That’s the figure you’ll be hauled in to explain come March.
Justifying indexation: which index, which month, which part
This is where justifying a contract budget goes wrong most often. Not every contract indexes the whole amount against the same index. There are three things you need to know per contract:
- Which index applies: CBS-CPI, a collective labour agreement wage index, the SCA wage index or a materials index. Labour-intensive services track the collective labour agreement, not the CPI
- Which reference month the contract specifies: the index level in, say, October determines the increase from 1 January
- Which part is indexed: often only the labour component, sometimes labour and materials separately, rarely the whole amount in one go
If those terms are scattered across dozens of separate PDFs, it costs you days of digging per budget round. And the controller then asks for a justification you can’t reproduce. The indexation clause should be findable alongside the contract itself, not in your head.
Invoice checking is the basis of a reliable forecast
Anyone who checks their invoices against the contract already has the building blocks for a substantiated forecast in place. The indexations actually applied, the booked and the outstanding additional work, the rejected invoice lines: that is exactly the data that makes your forecast reliable. In Excel this information lives on separate islands and you have to scrape it together again every year.
According to the sector body NEVI, roughly half of all contracts are not actively managed. For those contracts, the forecast is by definition a gamble. GRIP is contract management software for supplier contracts at Dutch organisations in healthcare, education and the public sector, and it links your invoice checking to the contract terms. What you check immediately becomes the justification for your next forecast. That’s the principle of connected contract data rather than separate files.
From separate Excel files to a reproducible justification
A forecast has to be explainable. To the controller, to the board and to the auditor. If you can no longer reconstruct how the figure came about in March, it’s a black box. And a forecast that deviates 8 per cent from the actuals means either overspending, or an unnecessarily high buffer that ties up money elsewhere.
That average 8 per cent gap between forecast and actual is exactly where justification pays off. Not because software is magic, but because you then know what you’re steering on. GRIP also saves organisations up to 30 per cent on contract administration, provided you genuinely approach contract management in a compliant way. The choice is simple: start your budget season with the index per contract, the outstanding additional work and the actual invoice data. Not with a percentage you add out of habit above the previous invoice.
Want to justify your 2027 contract budget with data you can account for? See how financial contract management in GRIP works, or book a demo and walk through one contract together.
Frequently asked questions
What is the difference between contract value and contract budget?
The contract value is the agreed price in the contract. The contract budget is what you actually spend in a financial year, including indexations, additional work and volume changes. The two amounts almost always diverge.
How do I justify a contract budget in a forecast?
Build the amount up from the actual terms: the index per component, the collective labour agreement increase, the outstanding additional work and expected volume changes. Use your checked invoice data as a starting point, not a general percentage above last year.
Which index applies to my cleaning contract?
That’s set out in the indexation clause of your contract. Labour-intensive services usually track a collective labour agreement wage index, not the CBS consumer price index. Often only the labour component is indexed, with materials against their own index.
Why doesn’t last year plus 3 per cent add up?
A general indexation percentage ignores the fact that collective labour agreement wages, materials and volume feed through differently. For labour-intensive contracts the wage component often rises faster than the general price index, so you forecast structurally too low.
How do I make my forecast explainable to the auditor?
Link every budgeted amount to the underlying contract terms and the actual invoice data. That way you can show per contract which index was applied, which additional work is included and how the total was built up.
What is outstanding additional work and why does it affect my forecast?
Outstanding additional work is work you agreed this year but haven’t yet invoiced. It falls outside the original contract value but does land in next year’s spend. Forget it, and you miss a real amount in your budget.
How secure is contract data in GRIP?
GRIP is ISO 27001 certified and processes contract data exclusively on European platforms, under European law. Your financial and contract data stays within the European Economic Area.