Variations in Construction Contracts in Vietnam: Decree 210 Rules

Updated: 22 October 2026 · IVLF Advisors

On many Vietnamese sites, from factory halls to hotel fit-outs and expressway packages, extra work starts on a verbal instruction and the paperwork follows months later, if at all. That is where unpaid claims, rejected payment applications and lender concern over budget overruns begin. Handling variations construction contract Vietnam projects now requires discipline: the Construction Law No. 135/2025/QH15 requires contract amendments to be in writing, and Decree 210/2026/NĐ-CP (Decree 210), effective 1 July 2026, requires that pricing principles for reasonable additional quantities be agreed before the work is done.

How Vietnamese law treats variations and contract amendments

Vietnamese law does not use the FIDIC word “Variation” as a term of art. It speaks of a contract amendment (sửa đổi hợp đồng) and of reasonable additional quantities (khối lượng phát sinh hợp lý). Decree 210 Article 3 describes the latter as work outside the agreed scope that arises during performance.

Article 84(1) of the Construction Law says an amendment covers adjustment of quantities, schedule, time, unit rates, contract price and other terms. It applies during the life of the contract and must be in writing. Decree 210 Article 22 adds a list of what an amendment may change:

• quantities, schedule, duration, unit rates and contract price;
• design;
• scope, technical requirements, quality, advance payment, payment, guarantees, insurance and warranty;
• contract type, pricing form, and the method and data source for price adjustment.

In practice, every variations construction contract Vietnam analysis starts with two questions. First, is the instruction inside or outside the agreed scope? Second, does the contract price type allow the change to carry a price at all? Our companion article on price adjustment in Vietnamese construction contracts covers the second question in depth.

Grounds for contract amendment: who can trigger a variation

Article 84(2) of the Construction Law lists the occasions on which the parties may agree an amendment. The table below puts those grounds next to the practical question of who normally drives each one.

Ground (Construction Law Art 84(2))	Typical trigger	Practical point
Change in State policy or law directly affecting performance	New regulation after signing	Check whether the contract allocates change-in-law risk expressly
Change in content, scope, technical requirements, quality, schedule, or advance and payment conditions	Employer instruction or contractor proposal	The commonest source of variations; needs written agreement
Force majeure (Art 13(1))	Natural disaster, epidemic, strike, embargo, archaeological find	Notice and impact assessment are required (Decree 210 Art 18)
Fundamental change of circumstances (Art 13(2))	Policy change or unforeseeable ground conditions	Civil Code conditions apply (Arts 156, 420)
Other cases agreed by the parties	Value engineering, programme recovery	Document the agreed basis

For public-investment and PPP contracts, Article 84(3) adds that the investor may decide an amendment that changes contract duration within the approved project duration, or that exceeds the package price (including contingency) without exceeding total investment. Force majeure and hardship amendments must keep the investment objective and scale and stay within total investment.

Additional work and change of scope under Decree 210 Articles 23 and 24

The legal consequence of a change of scope depends on the pricing form. The following rules for additional work in public-investment and PPP contracts come from Articles 23 and 24 of Decree 210. Private-capital contracts follow whatever the parties agreed.

• Lump sum: the price changes for reasonable additional work caused by an employer-requested scope change, by a contractor proposal that the employer accepts, or by force majeure or fundamental change.
• Fixed or adjustable unit rate: payment follows actual accepted quantity at the contract rate.
• Quantity moves by more than 20%: if the same movement also changes the contract price by more than 0.25% and the item rate by more than 1%, a new rate is agreed, applied to the excess above 120% for an increase, or to all accepted quantity for a decrease.
• Reasonable quantity with no existing rate: the parties agree a supplement to the contract; if they cannot, the law and procurement rules apply.

Article 23(3) is the sentence that protects both sides. For reasonable additional quantities, the parties agree a unit rate or pricing principles under Article 24 as the basis for the amendment before the work is carried out. Decree 210 Article 28(4)(k) repeats the same sequence for payment. Even where this rule is not mandatory for a private project, the sequence is an excellent standard for any contract.

The change of scope also tests the price form itself. A contractor under a lump-sum EPC contract carries design development risk inside the original scope, but not an employer’s new requirement. Disputes over variations construction contract Vietnam users face arise at the boundary, so the Employer’s Requirements and the baseline documents should be drafted so that the boundary can be found.

Variations in EPC and design-and-build contracts

Article 4 of Decree 210 states that in EPC, EP and EC contracts the design, scope and price are controlled together, that the contractor is fully responsible for design and equipment, and that payment follows milestones. The consequence is that design development inside the agreed scope is not a variation, however costly it becomes for the contractor. An employer’s change to its own requirements is a variation.

The FIDIC Silver Book follows the same logic, because the Contractor takes responsibility for the design and the Employer’s Requirements define the baseline. Market practice is to attach a short list of examples of what is and is not a variation to the Particular Conditions, because ambiguity at the boundary is the main source of EPC disputes.

Variations construction contract Vietnam: written instructions and authority

Variations construction contract Vietnam: who may instruct a change

The Construction Law’s writing requirement means that site meetings, emails between engineers and phone calls do not, on their own, amend a contract. Our recommendation, as market practice, is to treat three questions as conditions to any payment claim for extra work:

• Did a person with express authority under the contract instruct the work in writing?
• Does the instruction identify the scope, time effect and price basis?
• Did the contractor acknowledge it and record resources used from day one?

An employer’s supervising consultant (tư vấn giám sát) may be authorised to instruct, or may be limited to recommending. The contract should say which. Where the employer is a public body or a state-linked enterprise, internal approval of the investor may also be needed before a signature has legal effect, and that point should be checked before any work starts.

Record-keeping that wins payment

Contemporaneous records matter more than argument. Daily labour and equipment records, photographs, delivery notes and signed measurement sheets are the evidence a tribunal or auditor will accept. Under any variations construction contract Vietnam parties sign, contractors who wait for a final account to reconstruct variations usually recover less.

Procedure for a contract amendment: notices, replies and approvals

For public-investment and PPP contracts, Decree 210 Article 22(4) sets a procedure that is also a useful template for private deals:

1. The requesting party sends a written proposal stating its grounds and assessing the effect on schedule, price and quality.
2. The other party replies within seven working days. If it disagrees, it gives written reasons.
3. The parties negotiate and sign a written amendment. If they cannot agree, the employer organises the next step under procurement law.
4. If the amendment requires changes to the investment policy, feasibility study, design, total investment or estimate, the employer makes those changes before it signs the amendment.

Article 4 of Decree 210 supports the same logic: requests are written, and in public-investment and PPP contracts the reply is written, within the agreed period and no more than seven working days. Article 21 applies the same seven-day reply period to claims.

A variation that changes the completion date also raises an approval point. Under Article 25(2), where an adjustment would push beyond the approved project duration in a public-investment or PPP project, the investor must report to the decision-maker and obtain a decision on the project duration before the parties agree a revised contract schedule. We explain the time side separately in our article on extension of time in construction contracts in Vietnam.

Valuing, paying and securing a variation

Once a variation is agreed, payment follows the contract’s payment rules. For public-investment and PPP lump-sum contracts, Article 28(4)(c) of Decree 210 provides that payment is by percentage milestones and that the employer may not require detailed confirmation of completed quantities, except for work outside the agreed scope. A priced variation is therefore exactly the item that does need measurement. Article 87(2)(b) of the Construction Law requires the employer to pay in full and on time after deducting the advance and any agreed retentions.

Article 22(1) shows that an amendment can also change guarantees, insurance and warranty terms. A variation that materially increases the price should prompt a review of the performance guarantee amount, the insurance cover and the warranty period, so that security still matches the exposure.

FIDIC variation procedure compared with Vietnamese rules

Under the FIDIC 1999 edition, Sub-Clause 13.1 allows the Employer to initiate Variations at any time before the Taking-Over Certificate, by instruction or by requesting a proposal. In the Silver Book, a Variation cannot omit work to be carried out by others, and the Contractor must execute it unless it promptly notifies that it cannot readily obtain the Goods, that the change will reduce safety or suitability, or that it will adversely affect the Performance Guarantees. In the Red and Yellow Books, instructions are given through the Engineer (market practice and Clause 3 structure).

The FIDIC variation procedure in Sub-Clause 13.3 is more detailed than the Vietnamese baseline. If the Employer asks for a proposal, the Contractor responds with a description, a programme, and proposed changes to the Time for Completion and the Contract Price. The Employer approves, disapproves or comments, and the Contractor must not delay work while it waits. The valuation under Sub-Clause 3.5 includes reasonable profit.

Issue	FIDIC 1999 (Silver Book)	Vietnamese law
Form of change	Instruction or proposal request (13.1)	Written amendment (Construction Law Art 84)
Contractor input	Proposal with programme, time and price (13.3)	Written proposal with grounds and impact (Decree 210 Art 22(4) for public-investment and PPP)
Time effect	Extension under Sub-Clause 8.4(a), unless agreed under 13.3	Time and schedule adjusted by agreement (Art 25)
Valuation	Agreed or determined, with reasonable profit	Rates or principles agreed first (Art 23(3), Art 24)
Claim notice	28 days from awareness (20.1)	Agreed in contract; written claims; 7-day reply for public-investment and PPP

The chief difference is the status of an instruction. Under FIDIC, a valid instruction binds the Contractor and the price follows by determination. Under Vietnamese law, the starting point is a written agreement on the amendment, so a FIDIC-based contract governed by Vietnamese law should state clearly that an instruction under the variation clause is a written amendment for the purposes of Article 84, and should define who signs for each party.

FIDIC also offers tools Vietnamese statute does not detail: value engineering proposals at the Contractor’s cost (13.2), provisional sums used only as instructed (13.5) and daywork valuation where a daywork schedule is included (13.6). Using them requires the Particular Conditions to link them to the approval limits of the employer.

Risk allocation: where variations construction contract Vietnam disputes arise

Constructive and cumulative variations

The most expensive disputes concern a series of small instructions, none individually priced, that together change the sequence, resources and duration of the work. The contract should require a notice whenever the contractor considers that an instruction, drawing revision or approval delay is a change. Where it does not, the contractor risks losing the claim for lack of notice.

Lender and investor perspective

Lenders usually test variation exposure through contingency, change-control procedure and reporting. For a lump-sum EPC contract, the quality of the baseline documents largely determines how many variations will arise. A change that increases the price beyond the approved budget, or that alters the investment policy, may also need corporate or regulatory approvals before signature.

Practical checklist before instructing or accepting a variation

• Identify the contract clause and legal ground (Article 84(2)).
• Confirm the pricing form and whether a rate exists.
• Agree price principles and time effect in writing before work starts.
• Check delegated authority and any public-investment or PPP approvals.
• Record resources daily and keep notices within the contractual period.

Variations Construction Contract Vietnam: Infrastructure, Industry, Energy and Real Estate

Variations arise for different reasons in different sectors. Understanding the typical trigger helps decide who should be authorised to instruct a change and how fast the price must be settled.

Infrastructure and transport

On expressways, metro, high-speed rail and airport terminals, variations often come from ground conditions, third-party interfaces and owner-driven design changes. The North–South high-speed railway (about 1,541 km, through 15 provinces and cities per press reports of October 2026) and the Long Thành airport terminal (phase 1 operation expected from late December 2026) are examples of programmes where interface changes can multiply. Where the project is public investment or PPP, the Decree 210 procedures and reply deadlines may apply, and approval chains can be long; this depends on the funding source of each project.

Heavy industry and factories

For steel, cement, petrochemical and FDI factory projects, variations tend to follow process changes, equipment substitutions and schedule compression. These are private contracts where the parties agree; a clear variation authority matrix prevents unauthorised process changes.

Renewable energy and power

Solar, wind, grid and LNG-to-power projects face changes driven by grid-connection requirements and regulator or offtaker comments. A hypothetical grid-connection redesign should be treated as a priced variation, not as absorbed risk. Check electricity-sector rules.

Real estate

Resorts, hotels, urban areas and mixed-use complexes see tenant, operator and brand-standard changes. Operator-driven fit-out changes late in the programme are a classic source of cumulative variation claims, and housing buyers may add further requests.

Project type	Typical contract or risk feature	What to check
Expressway, rail, airport terminal	Ground and interface changes; approval chains	Decree 210 scope; who may instruct; reply deadlines
Factory or heavy-industry plant	Process and equipment changes	Variation authority matrix; price before work
Solar, wind, grid, LNG-to-power	Grid-connection and offtaker changes	Priced variation; link to offtake dates
Hotel, resort, mixed-use	Operator and tenant changes	Cumulative variation records; time impact

Conclusion

A variation is only as safe as its paper trail, and variations construction contract Vietnam practice rewards that discipline. Review your change-control clause now: make written amendment, agreed pricing principles and approval authority conditions of any extra work, then align them with Decree 210 and, where relevant, the FIDIC Particular Conditions.

Frequently Asked Questions

Must a variation be in writing in Vietnam?

Yes. Article 84 of the Construction Law requires contract amendments to be in writing. A verbal site instruction is a high-risk basis for any claim.

Can a contractor refuse an instructed variation?

Under the FIDIC Silver Book, only on stated grounds: goods unavailable, reduced safety or suitability, or harm to Performance Guarantees. Under Vietnamese law, the contract and written agreement govern.

Must the price be agreed before extra work starts?

For public-investment and PPP contracts, pricing principles for reasonable additional quantities must be agreed before execution. Private contracts follow their terms, but the same sequence is prudent.

How quickly must a variation proposal be answered?

In public-investment and PPP contracts, within seven working days, with written reasons for any refusal. Private contracts follow the agreed period.

Does a variation extend the time for completion?

Only if time is adjusted. Under FIDIC Sub-Clause 8.4(a) a Variation gives an extension unless time was agreed under 13.3. Under Vietnamese law the parties adjust schedule by agreement.

Disclaimer: This article provides general information only and is not legal advice for any specific matter. It reflects Vietnamese law as of 22 October 2026. Please obtain advice on your own facts before acting.