Limits on changing a public contract: 15 and 50 per cent

RHS § 123(1) lists the cases in which a hankeleping (public contract) may be modified without a new procurement procedure. Each case has its own conditions; some have a value limit, some do not.

Point	Case	Conditions	Value limit for construction works
point 1	small change	the overall nature of the contract does not change	the total value of changes does not exceed the international threshold or 15% of the original value
point 2	change provided for	the scope, content and conditions, “for example on price review”, were provided for in the procurement documents “clearly, precisely and unequivocally” (unofficial translation)	no limit
point 3	additional works from the same tenderer	a change of tenderer would cause significant inconvenience or a considerable increase in costs and would be impossible for economic or technical reasons (from 1 November 2026: unreasonable)	no single change increases the value by more than 50% of the original value
point 4	unforeseeable circumstances	circumstances that “a diligent contracting authority” could not have foreseen; the overall nature of the contract does not change	50% per change
points 5 and 6	replacement of the tenderer	in the cases set out in the law	not covered in this article
point 7	non-substantial change	the change is not substantial within the meaning of subsection 2	the criteria of subsection 2

Point 1 is cumulative; points 3 and 4 apply change by change. The 15% for small changes applies across the whole contract; once it is used up, the next small change cannot be made under that point. The limit in points 3 and 4 applies to each change separately, but their conditions are stricter: for additional works, a change of tenderer must be justifiably ruled out; for unforeseeable circumstances, the hankija (the contracting authority) must show that a diligent contracting authority would not have foreseen them.

The amount of the international threshold is not given here. The law refers to the amount set by the European Commission and published in the register (§ 14(3)); the amount in force can be found in the procurement guide and the register.

Point 2 is the only lever without a value limit, and it has to be created before the procurement. A price review clause or a clause on options for works that is precise enough in the procurement documents allows the contract to be changed without using up any percentage. Drafting that clause is covered in the article on price review and indexation in a public contract.

Under point 7, only what is not substantial can be changed, and the law says what is substantial. Under § 123(2), a change is substantial in particular when:

• it introduces conditions that would have allowed other participants or wider competition in the original procedure;
• it changes the economic balance of the contract in favour of the tenderer in a way the contract did not provide for;
• it considerably extends the scope of the contract;
• the tenderer is replaced other than as provided for in points 5 and 6.

From the contracting authority's point of view, the second criterion is the most dangerous. A change that improves the contractor's terms without anything in return, such as raising the fee for the same work, shifts the economic balance in favour of the tenderer. Such a change needs a ground in points 1 to 4; it cannot be made under point 7.

The distinction between additional work and changed work, important in the private sector, also matters in a public contract, but for a different reason. According to the Supreme Court case law review, the trend in case law treats as lisatöö (additional work) work outside the subject matter of the contract that requires agreement; muudatustöö (changed work) falls within the subject matter of the contract but is carried out differently from what was agreed. That distinction is explained in the article additional work or changed work: why the difference matters.

For a contracting authority, additional work almost always means a § 123 modification. New work that was not part of the subject matter of the contract increases the value and must fit within the limits of point 1, 3 or 4 if it was not provided for in the procurement documents. Changed work may stay within the framework of the contract if the price does not change, but a price change must likewise be justified under § 123. Classifying the work in writing at the moment it is ordered therefore gives the contracting authority double protection: under the contract and under the law.

If the contract includes indexation, the limits in points 1, 3 and 4 are calculated from the indexed amount (§ 123(4)). This is no minor technicality: when construction prices rise, the amount from which 15% and 50% are calculated rises too.

A fictitious example shows how the cumulative limit is used up. The original value of a public works contract is 2,000,000 euros excluding VAT.

Step	Change	Cumulative amount under point 1	Share of the original value
1	extra sockets and cabling	€140,000	7.0%
2	change to a facade detail	€250,000 (140,000 + 110,000)	12.5%
3	external lighting, €80,000	€330,000	16.5%: does not fit within point 1

For the third change, only 50,000 euros remain under point 1, because 15% of 2,000,000 euros is 300,000 euros. The third change must be justified under point 3 or 4, if their conditions are met, or a new procurement must be organised. If the contract included indexation and the indexed value were 2,080,000 euros, the 15% limit would be 312,000 euros and the remainder 62,000 euros; the third change would still not fit.

The limit in points 3 and 4 is larger, but not free. In the same example, no change for additional works or unforeseeable circumstances could increase the value by more than 1,000,000 euros (50% of the original value), or by more than 1,040,000 euros for an indexed contract. But a statutory limit is not funding: the contracting authority has to pay for every change, and the changes add up in the final cost.

A modification notice must be submitted to the register for a change made under points 3 and 4 (§ 123(5)). Until 31 October 2026 the time limit is 10 days; from 1 November 2026 it is 30 days.

An impermissible change gives the contracting authority the right to leave the contract. Under RHS § 124(1)(1), the contracting authority may terminate the contract or withdraw from it if the contract has been modified in a way § 123 does not allow. The provision is a right of the contracting authority, but in practice it means a crisis: an unfinished build, a new procurement and a final cost no longer under control.

That is why three things are worth documenting for every change: under which point the change is made, why its conditions are met, and what the cumulative amount is after the change. The same information is needed for the modification notice and in the event of an inspection.

A register of changes is the contracting authority's first line of defence. For each change it records the amount, the ground (point), the date and the cumulative share of the original or indexed value. When the remainder under point 1 falls below the size of the next expected change, it is time to decide whether the works can be carried out on another ground, postponed or procured separately.

A contingency is not a right to change. The contracting authority may plan a reserve in its funding for unforeseen costs, but having a reserve does not make a change lawful. The reserve answers the question “do we have the money”, § 123 the question “do we have the right”.

The cheapest change is the one provided for in the procurement documents. If the contracting authority knows that certain works may be needed, it can describe them in the procurement documents as an option within the meaning of point 2. The price is then set in competition and the change does not use up the 15% limit.

Until 31 October 2026 the current rules apply. The Act amending the Public Procurement Act and other Acts (RT I, 03.07.2026, 3) enters into force on 1 November 2026 and changes § 123 in two places.

Provision	Until 31.10.2026	From 01.11.2026
§ 123(1)(3)	“nor would it be possible for economic or technical reasons”	“and would be unreasonable for economic or technical reasons”
§ 123(5)	modification notice within 10 days	modification notice within 30 days
15% and 50% limits	apply	unchanged

The change to point 3 is one of substance. “Impossible” gives way to “unreasonable”, which on its wording is a lower threshold: where the new version applies, ruling out a change of tenderer no longer requires showing that it is impossible, only that it would be unreasonable for economic or technical reasons. The 50% limit stays the same, however.

The transitional provision concerns procedures, not contracts directly. Under § 219^3, procurement procedures begun before 1 November 2026 are completed under the version in force until 31 October 2026. The text of the Act does not expressly govern the modification after that date of public contracts already signed. If a change is made after 1 November to a contract signed under the previous rules, the applicable version must be assessed legally before deciding. The transition and ongoing procurements are covered in the article on the transition and ongoing procurements, and the reform as a whole in the overview of the procurement reform; the reform enters into force on 1 November 2026. The general overview of the contracting authority's levers in this branch is in the article the public works contract: price, changes and limits.