Modifying a public contract after award: when is it a substantial modification?

Can a public contract be changed after award?

Yes, but only within limits set by the law itself. The main rule in the Dutch Public Procurement Act 2012 (Aanbestedingswet 2012) is in Article 2.163a: a public contract that changes substantially during its term has to be tendered again. The exceptions are in Articles 2.163b to 2.163g. According to PIANOo, the Dutch public procurement expertise centre, that list is exhaustive. If a change fits none of those grounds, it cannot be made without a new tender.

The rules come from Article 72 of Directive 2014/24/EU, so the same structure applies across the EU. They cover contracts tendered under the EU rules. For contracts below the EU threshold they do not apply, according to PIANOo. There, Dutch courts test changes against the general principles of procurement law, such as equal treatment and transparency.

Worth knowing: the buyer decides whether a change is allowed, not you. But you carry out the work and invoice it. If a change goes wrong, it affects you too.

Which changes does the law allow?

If the buyer wrongly relies on unforeseen circumstances for a change, an interested party such as a competitor has thirty calendar days to seek annulment in a Dutch court if the change was published on TenderNed, and six months if it was not, according to PIANOo.

What is a substantial modification?

A substantial modification is a change that makes the contract materially different from the one originally tendered. Article 2.163g, following Article 72(4) of the directive, names four situations where that is always the case. The first three come from the Pressetext judgment of the EU Court of Justice (C-454/06, 19 June 2008), on which Article 72 of the directive builds.

• Different marketOther bidders or another winnerThe change introduces conditions that, had they been in the original tender, would have attracted other candidates or led to a different winner.
• Economic balanceShifted in your favourThe economic balance shifts in favour of the contractor in a way the original contract did not provide for. For example a higher price for the same work, without a clause allowing it.
• ScopeConsiderably more workThe scope of the contract is extended considerably, with work that was not part of the original contract.
• ContractorA different companyA new contractor takes over the contract, outside the cases of Article 2.163f.

Not every change counts. PIANOo gives as marginal changes without consequences a different project manager, a different way of invoicing and a marginal price change, as long as price and the nature of the work stay essentially the same. What applies if you want to replace a subcontractor or consortium partner, read in consortium and subcontracting.

The test is always the same: would the market have bid differently if this change had been in the documents from the start?

How does the de minimis rule work?

The de minimis rule in Article 2.163b allows small changes without further testing. The value of the change must meet three conditions at once: below the applicable EU threshold, below 10% of the original value for supplies and services or 15% for works, and no change to the overall nature of the contract. With several changes, PIANOo says the net cumulative value counts.

If the contract has an indexation clause, the indexed value is the starting point for the percentages. That is in Article 72(3) of the directive, and the Dutch legislator adopted it in Articles 2.163b and 2.163d.

A fictional example. A Dutch municipality has a cleaning contract worth €600,000 over its full term. Ten percent of that is €60,000, well below the €216,000 threshold for services bought by local and regional authorities. In year two a building is added, worth €45,000. That fits. A year later a second building follows, worth €25,000. Together that is €70,000, more than 10%. The second extension no longer fits under the de minimis rule.

What does this mean for extra work and extra volume?

Extra work (in Dutch contracts often called meerwerk) is a contract term, not a term from procurement law. For procurement law, extra work is simply a modification of the contract, and it has to fit one of the grounds. The buyer preferring to give the work to you is not a ground.

If the extra work fits under the de minimis rule or a review clause, it is usually simple. If it is larger, additional work or unforeseen circumstances come into play, with the 50% limit per modification and publication on TenderNed. For additional work it must also be clear that another contractor is not an option for economic or technical reasons. That is hard to argue for an extra district of grounds maintenance or an extra cleaning location, because another company could do that just as well.

Another fictional example, this time works. A contractor is building a pumping station for a water authority, worth €2,000,000. During construction an extra foundation turns out to be needed, which was not in the specifications. If it costs €250,000, that stays below 15% and below the €5,404,000 threshold for works, and fits under the de minimis rule. If it costs €600,000, Article 2.163d or 2.163e comes into play, and the buyer has to publish the change.

Under a framework agreement the maximum volume is the limit. Once that maximum is reached, more cannot be added without limit. So do not count on revenue above the maximum stated in the documents.

Does indexation count as a modification?

Indexation that is in the tender documents is not a modification but performance of the contract. PIANOo names price indexation as an example of a review clause. How to work out an indexation clause, read in price indexation.

It is different when prices rise faster than the clause covers, or when there is no clause. A price adjustment in a running contract then has to fit the contract and the modification grounds of the Public Procurement Act, and may not be a substantial modification, PIANOo writes. A higher price for the same work shifts the economic balance in your favour. Without a clause, that is in practice mostly possible within the de minimis rule or in genuinely unforeseen circumstances. If you ask for an adjustment yourself because of unforeseen circumstances or force majeure, PIANOo says you have to show that the contract cannot stay as it is.

PIANOo advises buyers to record such a price adjustment in writing, preferably for a limited period in an addendum, with review moments. So expect that an adjustment may be temporary.

What do you do as the contractor?

1. 1Read the change provisions before you bidLook in the draft contract for extra work, indexation, options, extensions and replacement. If there is nothing, anything you want to change later depends on the narrow legal grounds. How to go through the documents quickly, read in reading tender documents.
2. 2Ask for a review clauseIf there is no arrangement for price rises, volume growth or extra work, raise it in the clarification round (in Dutch the nota van inlichtingen). A review clause has to be in the original tender documents. After award it cannot be added.
3. 3Record every change in writingWhat, why, for what amount, on which ground and at which price level. A verbal instruction for extra work is a risk, for getting paid and for the lawfulness of the change.
4. 4Keep countAdd up all changes and set them against the original, possibly indexed, value. As the total approaches 10% or 15%, discuss with the buyer which ground the next change rests on.
5. 5Ask about the ground for large changesFor additional work or unforeseen circumstances, ask whether the buyer will publish the change on TenderNed. For a change based on unforeseen circumstances, PIANOo says a competitor has thirty calendar days after publication to seek annulment, and six months without it.

The best change after award is the one that was already in the documents.

Are the rules about to change?

Possibly, but not yet. On 9 September 2026 the European Commission published a proposal for a regulation on public contracts and concessions, COM(2026) 590, which is meant to replace the current procurement directives. It is a proposal: the European Parliament and the Council still have to decide on it. Until new rules apply, Article 72 of the directive and, in the Netherlands, Articles 2.163a to 2.163g of the Public Procurement Act 2012 remain in force.