Why the form number matters

Australian Standard contracts come in two broad flavours: construct only, where you build to someone else's design, and design and construct, where you carry some or all of the design. They also split into head contracts, signed between the principal and the main contractor, and subcontracts, signed between the main contractor and you. Main contractors usually pass their head-contract obligations down the chain back-to-back, so risk written into the top contract can flow through to yours. For more on that, see the subcontract clauses that quietly shift risk.

1. AS 2124-1992: the original general conditions

AS 2124 is the older construct-only head contract, administered by a superintendent. It has largely been overtaken by AS 4000, but is still used on some jobs, so you may see subcontract terms drawn from it. Its notice and time-bar provisions are strict and the older wording can catch people out, so read the claims clauses closely if a job is built on it.

2. AS 4000-1997: the construct-only workhorse

AS 4000 is the most common construct-only general conditions form in Australia and the base most main contractors work from. A refreshed edition, AS 4000:2025, was released in 2025. If your job sits under AS 4000, it is worth understanding how the superintendent, notices and payment claims work. We break it down in AS 4000 explained for subcontractors and cover the update in what changed in AS 4000:2025.

3. AS 4901-1998: the subcontract you'll most often sign

AS 4901 is the subcontract conditions form that sits under a construct-only head contract like AS 4000 or AS 2124. For most subbies on a construct-only job, this is the form you actually sign. It mirrors a lot of the head-contract machinery (superintendent's directions, variations, extensions of time and progress claims), but the version handed to you is often amended in the main contractor's favour. Before you sign, work through what to check in AS 4901 subcontract conditions.

4. AS 4902-2000: the design and construct head contract

AS 4902 is the general conditions for design and construct, where the contractor takes on design responsibility as well as building the works. It is a head contract, so you would not usually sign it directly, but if the main contractor is on AS 4902, some design and coordination obligations may be pushed down to you, along with insurance and professional indemnity expectations.

5. AS 4903-2000: the design and construct subcontract

AS 4903 is the subcontract that sits under an AS 4902 head contract. If you are a subcontractor on a design and construct job and you carry any design, even shop drawings or a design portion, this is the form you are likely to see. Watch the design responsibility, professional indemnity insurance and novation provisions carefully, because they can shift more liability onto you than a straight construct-only subcontract.

6. AS 4906-2002: minor works (and its subcontract, AS 4905)

AS 4906 is the minor works head contract, administered by the principal and meant for smaller or lower-risk jobs. The matching minor works subcontract is AS 4905. The paperwork is lighter, but that cuts both ways: fewer formal steps can mean less protection if a small job goes sideways, so keep your records tight even when the contract feels casual.

How to tell which form you're on

Before you price or sign, take two minutes to work out exactly what is in front of you:

  • Check the cover sheet or formal instrument for the AS number and year.
  • Work out whether it is construct only or design and construct. Design and construct usually means AS 4902 or AS 4903.
  • Confirm whether you are signing a head contract or a subcontract. As a subbie you will usually be on AS 4901, AS 4903 or AS 4905.
  • Look for words like amended, special conditions or a schedule of departures. The standard form is rarely handed over unchanged.
  • Compare the notice and time-bar clauses against what you can realistically do on site. See delay notice time limits.

What to do before you sign

Once you know the form, read the clauses that decide how you get paid and how you protect a claim: variations, extensions of time, progress payments and any time bars. If the wording is dense, our free tools can help you organise what to check, and if you need to chase payment, make sure you get a Security of Payment claim right. None of this replaces your own legal advice, but it means you sign with your eyes open.

Knowing your form number will not win an argument on its own. But it tells you exactly which notice, claims and payment clauses govern the job, so you can price the work, keep the right records and raise anything that looks off before you sign.