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What is a variation and can a builder charge whatever they like?

The short answer

A variation is a change to the contracted scope. In most states it must be in writing, priced and signed before the work is done, and a builder who does the work first is on weak ground claiming for it.

TradieAnswers editorial · written in-house and sourced to the authorities listed below

Checked against 5 published sources, listed in full at the end of this page. How we source this

Variations are normal. Renovation in particular uncovers things nobody could see, and a project without any variations is unusual. What is not normal is a variation that appears as a line on an invoice after the work was done, with no prior agreement on price.

The general requirements

  • In writing, describing the change specifically rather than in general terms.
  • Priced, with the effect on the contract sum stated.
  • The effect on the completion date stated, since variations are also the usual explanation for delay.
  • Signed by both parties before the work is carried out.

When it arrives afterwards

A builder who carries out a variation without complying with the state's requirements generally cannot recover for it as of right, though most legislation lets a tribunal allow payment where it would be unfair not to, for instance where you asked for the change and clearly benefited. That is a discretion, not an entitlement, which is why the paperwork matters to them as much as to you.

Who does this work

You can probably handle this yourself

Because this is a contract question, and the requirement for variations to be in writing is set by your state's building contract legislation.

This work is licensed, though the threshold and the licence class differ between states. Check a licence in your state

Where are you?

Who regulates building in your state

Trade regulation in Australia is state law, so the body that answers this depends on where the work is. Pick yours.

New South Wales — NSW Fair Trading
Licenses builders and trade contractors. A licence is required above a value threshold, and home building compensation cover is required above a higher one. How to check a licence in NSW
Victoria — Building and Plumbing Commission
Took over from the Victorian Building Authority on 1 July 2025, bringing licensing, enforcement, insurance and dispute resolution under one body. How to check a licence in VIC
Queensland — Queensland Building and Construction Commission
Licenses builders and trade contractors, administers the Queensland Home Warranty Scheme, and handles defect complaints. How to check a licence in QLD
Western Australia — Building and Energy
Registers builders and building surveyors, and handles building service complaints. How to check a licence in WA
South Australia — Consumer and Business Services
Licenses building work contractors and supervisors, and maintains the public register. How to check a licence in SA
Tasmania — Consumer, Building and Occupational Services
Licenses building services providers, including builders, under the Building Act 2016. How to check a licence in TAS
Australian Capital Territory — Access Canberra
Builders and building assessors are licensed under the Construction Occupations (Licensing) Act 2004. How to check a licence in ACT
Northern Territory — Building Practitioners Board
Registers building practitioners and publishes the register of who currently holds registration. How to check a licence in NT

What to ask

  1. Ask for the variation in writing, with the scope and the price, before the work is done rather than after.
  2. Ask which clause of the contract the variation is made under.
  3. Ask whether it changes the completion date, and get that in writing too.
  4. Do not pay for a variation that was never documented until you have checked your state's rules on what a builder can recover for undocumented variations.

Sources

Every source below was fetched and its response recorded on the date shown. Where a government site blocks automated clients, that is noted rather than reported as a successful check.

  1. Building contracts · Consumer Affairs VictoriaChecked 2026-08-10 · responded 200 OK
  2. Building Commission NSW · NSW GovernmentChecked 2026-08-10 · responded 200 OK
  3. QBCC · Queensland Building and Construction CommissionChecked 2026-08-10 · responded 200 OK
  4. Victorian Civil and Administrative Tribunal · Victorian Civil and Administrative TribunalChecked 2026-08-10 · responded 200 OK
  5. NSW Civil and Administrative Tribunal · NSW Civil and Administrative TribunalChecked 2026-08-10 · responded 200 OK

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