Neither concept is in the law
The chapter of the Law of Obligations Act (võlaõigusseadus, VÕS) on the contract for work (§§ 635 to 657) uses neither the term additional work nor the term changed work. The law speaks of the contractor (töövõtja), the client, the work, the remuneration and the estimate, but not of how to tell work added to the contract apart from work carried out differently within it. The concepts have come from construction practice and case law.
A convenient summary is the Supreme Court (Riigikohus) case-law review "Töövõtuleping" ("Contract for work", 2022, status at 01.01.2022). The review itself states that it is not an official source of the Supreme Court's positions; what follows is therefore the trend of published decisions, not a rule laid down by statute. On changed works, the review also refers to the general conditions for construction contracts ETÜ 2013 (point 1.17), which are the sector's general terms; whether they apply in a given contract depends on whether the contract refers to them.
Additional work: outside the subject matter of the contract
According to the Supreme Court case-law review, additional works are works that fall outside the subject matter of the contract and require an agreement of the parties. Without such an agreement, the contractor is not entitled to payment for those works under the contract. Additional work is in substance a new order attached to the existing contract: like any other order, it needs the client's consent.
For the client, this means that the duty to pay for additional work starts with its own decision. If the client neither ordered the work nor agreed to it being done, the contractor has no contractual basis to claim payment for it. Whether the contractor might have some other claim depends on the circumstances of the case; in any event it does not arise from the contract.
Technical necessity does not automatically make work part of the price. According to the review, the mere fact that work should have been included in the tender, or that it was technically necessary, does not prove that it was within the contract price (Supreme Court judgment of 19.12.2017 no 2-15-15662/55, para 13; judgment of 20.09.2017 no 2-13-40856/124, para 14). The client therefore cannot refuse a claim for additional work simply by arguing that "it could not have been built without it". It has to show that the work belonged to the agreed subject matter of the contract.
Changed work: within the subject matter, but done differently
According to the review, changed works stay within the subject matter of the contract but are carried out differently from what was agreed. For example, the material, the solution or the method of execution changes, but the work itself belonged to the contract from the start. The client has already agreed that this work will be done; the only new question is how.
With changed work, the dispute is not about the duty to pay but about the price difference. The price of the planned execution has to be compared with the price of the actual execution. The difference may be in the contractor's favour, but also in the client's favour if the new solution is simpler or cheaper. A client who treats a change only as an extra cost forgets that a price reduction is also part of the change.
Whether work is additional or changed is determined by interpreting the agreement of the parties. Under VÕS § 29, the actual common intention of the parties comes first (subsection 1). If it cannot be established, the contract is read as a reasonable person would understand it (subsection 4). Account is taken, among other things, of pre-contractual negotiations, the conduct of the parties, the usual meaning of terms in the field and practices (subsection 5), and the contract is interpreted as a whole (subsection 6).
Why the difference matters: a comparison
The same extra invoice means an entirely different risk for the client depending on which category it falls into.
| Question | Additional work | Changed work |
|---|---|---|
| Did the work belong to the subject matter of the contract? | no | yes, but in a way that differs from what was agreed |
| Does the client owe payment without an agreement? | according to the review, not under the contract | payment for the work has already been agreed; the question is the price difference |
| What is the dispute about? | whether the client ordered the work and at what price | how far the actual execution differs from the planned one |
| What must the client show? | that it did not agree, or on what terms it agreed | what the contract originally provided |
| What helps avoid a dispute? | a written agreement before the works start | a written price difference and effect on the deadline before the works start |
A binding estimate does not protect the client against additional work, because additional work lies outside the estimate. VÕS § 639(1) presumes that the estimate (eelarve) agreed in the contract for work is binding, and according to the review, where the estimate is binding the contractor cannot claim payment above it (2-15-15662/55, para 12). That protection covers the agreed work. Additional work is a new agreement whose price is added to the estimate if the client orders it. Both concepts must therefore be read together: the binding estimate closes the price of the subject matter of the contract, and a written procedure for additional works closes the door on additions without agreement.
The client's design and its own responsibility
The client is responsible towards the contractor for the design it supplies itself. According to the review, the client is responsible for the conformity of the design it has provided (2-15-15662/55, para 19; the review also refers to ETÜ 2013 point 3.1.1). If a change is needed because the design was defective or inconsistent, the contractor did not cause it.
In that case the client's question is a different one: not "should I pay" but "from whom can I recover it". If the design was prepared by a designer (projekteerija) on the client's order, recovery depends on the contract between the client and the designer. Classifying the change as additional or changed work with the contractor does not answer that question, but it lays the groundwork for it: the change order must record what caused the change.
Method: classify in writing when the request is made
The classification must be recorded at the moment the change is requested or claimed, not when the invoice arrives. Later, each party is a prisoner of its own memory and interests. A written change order should contain at least the following.
| Element | Content | Why it is needed |
|---|---|---|
| Classification | additional work, changed work, or part of the contract already being paid for | decides whether the client pays and what the dispute is about |
| Description | exactly what changes or is added, with a reference to the drawing sheet or document | links the change to the contract documents |
| Cause | the client's wish, a design error, an unforeseen circumstance on site | shows whether the client can pass the cost on to someone else |
| Price or pricing method | a fixed amount or an agreed calculation method | without it the agreement is incomplete |
| Effect on the deadline | a number of days or "no effect" | any later dispute over delay starts here |
| Signatures | the client's authorised person and the contractor | proves the agreement |
If the parties cannot agree on the price, that too must be written down. The change order can state that the work will be done and the price agreed later according to a set calculation method, or that the client does not accept the classification and reserves the right to challenge it. An unrecorded disagreement later looks like consent, because the conduct of the parties is a relevant circumstance when interpreting a contract (VÕS § 29(5)).
The document has to be easy to find. Where the decision on a change must be recorded, whether in a separate change order, in the minutes of a site meeting or in the construction works diary, and who signs it, is explained in the article on construction records as evidence.
What to write into the contract
Since the law does not define the concepts, the contract can. The client gains most when the contract states expressly what is additional work and what is changed work, rather than leaving it to later interpretation. Useful clauses include the following:
- a list of the documents forming the subject matter of the contract and their order of precedence;
- a definition of additional work and changed work that follows the distinction described above;
- a requirement that no additional work starts before a written agreement, except work needed to remove a hazard, which is notified immediately;
- a list of the client's representatives entitled to order a change, with a financial threshold above which the signature of the client's management is required;
- a deadline for the contractor to submit the price of a change and its effect on the programme after the client's request;
- a principle for calculating the price of changes, agreed before the first change.
Standard terms drafted by the contractor often take the opposite approach. For example, a clause may allow the contractor to carry out "necessary works" and invoice them later, or treat the client's silence as consent. Such a clause should be amended or removed before signing.
Contracting authority: agreement is not enough
For a public contract, an agreement on additional work is also a modification of the public contract (hankelepingu muutmine), and the Public Procurement Act (riigihangete seadus, RHS) limits it. RHS § 123(1) allows a public contract to be modified without a new procurement procedure only in the cases listed there. One of them is additional construction works with the same economic operator where a change of operator is not possible for economic or technical reasons and would cause significant inconvenience or substantial additional costs; no such modification may increase the value of the public contract by more than 50 per cent of the original value (point 3). Smaller modifications are allowed if the total value of the modifications does not exceed the international threshold or 15 per cent of the original value of the works and the overall nature of the public contract does not change (point 1).
Until 31 October 2026, the current rules apply. From 1 November 2026, the point 3 condition "would not be possible" is replaced by the wording "would be unreasonable" (unofficial translation), and the deadline for submitting the modification notice is extended from 10 days to 30 days; the 15 and 50 per cent limits stay the same. All cases and how they are calculated are described in the article on limits on changing a public contract: 15 and 50 per cent.
What this article does not cover
Calculating the price of a change belongs to the budgeting guide. How to price a change using the budget structure and unit rates is described in the article on variations and additional works, and how to track the effect of a change on the budget lines in the article on tracking at line level. This article deals only with whether, and on what basis, the client pays.
This article describes the state of the rules and published case law on the date of checking and is intended for professional orientation. It does not replace legal advice or a review of the specific case.