When a business engages a supplier for a significant piece of work, the conversation often jumps straight to price: can we get a fixed price? The question is understandable. A single number is easy to approve, easy to budget for and easy to compare between suppliers. It appears to move the risk of cost overruns onto the supplier. For many purchases, it is exactly the right answer.
But “fixed price” is often used as if it describes the whole arrangement, when it only describes one part of it. Two separate decisions are being made. The first is the delivery model: who designs, who builds, who integrates the parts and who manages the interfaces between them. The second is the pricing method: how money is calculated and how the financial consequences of uncertainty are shared. Mixing them up leads to arrangements where the right supplier is asked to work under a pricing method that does not fit the work, or where a familiar pricing method forces an awkward delivery arrangement.
This article explains the difference between the two decisions, the main pricing methods and what each one does with uncertainty, why fixed price remains popular and when its simplicity is real, and how both buyers and suppliers can choose a pricing method the work can genuinely support. It is general information. For significant contracts, take advice from a lawyer or an experienced commercial adviser.
Two decisions, not one
The delivery model describes how the parties work together. Common examples include:
- Buyer designs, supplier builds: the buyer, or a designer it engages, produces the design, and a supplier builds or supplies to that design.
- Design and build: one supplier is responsible for both designing and delivering the result, usually against a performance requirement.
- Packages under the buyer’s management: the buyer splits the work into several packages and coordinates them, sometimes with help from a project manager.
- Collaborative arrangements: buyer and supplier work closely as one team and share some of the risk and reward.
The pricing method describes how the supplier is paid and who bears the cost if things turn out differently from expectations. A design-and-build arrangement can be priced as a fixed lump sum, on a target cost or in stages. A package arrangement can use a different pricing method for each package.
A useful sequence is:
- Sourcing boundary: what will the business do itself, and what will it buy?
- Delivery model: how will the parties work together, and who owns design and integration?
- Pricing method: how will cost uncertainty be shared?
- Contract controls: what mechanisms will manage performance, change and exit?
Working through these in order stops the pricing method being used as a substitute for thinking about delivery.
The main pricing methods
| Method | How the supplier is paid | Who carries cost uncertainty | Suits |
|---|---|---|---|
| Fixed price (lump sum) | One agreed price for a defined scope | Mostly the supplier, within the defined scope | Well-defined, repeatable work with little expected change |
| Schedule of rates | Agreed rates per unit, multiplied by actual quantities | Shared: supplier carries rate risk, buyer carries quantity risk | Work whose type is known but whose quantity is not |
| Time and materials | Agreed hourly or daily rates plus materials, often with a cap | Mostly the buyer | Work that cannot be defined in advance, such as investigation or urgent repairs |
| Cost reimbursable (cost plus fee) | Actual costs, shown openly, plus a fee | Mostly the buyer | Highly uncertain work where the buyer can oversee costs |
| Target cost | Agreed target; overruns and savings shared in agreed proportions | Shared, by formula | Uncertain work where both parties can influence cost |
| Staged | Early stage on rates or a small fixed fee; later stage fixed once defined | Shifts from buyer to supplier as uncertainty falls | Work that becomes well defined only after investigation or design |
Two terms often appear alongside these. A provisional sum is an allowance included in a price for work that cannot yet be defined, to be adjusted once the actual cost is known. A cap or not-to-exceed amount limits what the buyer will pay under a time-and-materials or cost-reimbursable arrangement without further approval. In residential building, some states regulate how allowances such as provisional sums and prime cost items must be used and disclosed, so check the rules in your state if they apply.
Why fixed price persists
Fixed price is sometimes described as old-fashioned. It persists because it solves several real problems at once:
- Financial simplicity: the owner or board sees a defined commitment that fits a budget and an approval limit.
- Administrative simplicity: the supplier manages its own costs, so the buyer does not need to inspect them.
- Comparison simplicity: where several suppliers price the same scope, their offers can be compared directly.
- Clear accountability: one party has committed to deliver the scope for the price.
These advantages are genuine. The question is whether the conditions of the work support them.
What fixed price does not do
Fixed price is often treated as stronger protection than it is. Four limits matter:
- Suppliers price the risk. A supplier asked to carry uncertainty will include a contingency for it. If the work is uncertain, the buyer pays for that contingency whether or not the risk occurs.
- Price certainty is not outcome certainty. A fixed price covers the defined scope. Anything outside it, including work the buyer assumed was included, becomes a variation. Uncertain work priced as a fixed lump sum often produces many variations.
- Pressure can move to quality. A supplier losing money on a fixed price may look for savings in materials, testing, documentation or attention.
- Defining the scope costs time and money. Fixed price needs a defined requirement before award. That definition work is real, and skipping it does not remove the uncertainty. It only hides it.
A wide spread between quotes for the same fixed-price scope is often a signal that the scope is not as well defined as the buyer thinks. Different suppliers are pricing different assumptions.
When fixed price fits
Fixed price is most likely to give good value when most of these conditions hold:
- Definition: the scope and required performance are mature and clearly described.
- Competition: several suppliers can price the same requirement.
- Repeatability: the market understands the work and has done it many times.
- Low change: major changes during delivery are unlikely.
- Supplier capacity: suppliers can carry the cost risk without excessive contingency or financial strain.
- Buyer priority: the buyer places a high value on certainty and simple administration.
Where several of these are weak, consider another method, at least for the uncertain parts of the work.
The other methods need oversight
The alternatives to fixed price usually fit uncertain work better, but they ask more of the buyer.
- Time and materials needs someone to check that hours and materials are reasonable and that the work is progressing. Without a cap or regular review, costs can drift.
- Cost reimbursable needs open-book records, agreement on which costs are allowable and the ability to review them. A buyer who cannot or will not check costs should be wary of this method.
- Target cost needs a well-founded target, a clear formula for sharing overruns and savings, and agreement on how the actual cost will be measured. If the target is set too high, the supplier earns a share of savings that were never real.
- Schedule of rates needs a reliable way of measuring quantities.
The question is not only which method fits the work, but whether the business has the people and systems to administer it. The designing incentives that enforce themselves article looks at how payment structures shape behaviour.
Different parts, different methods
Larger projects usually contain several kinds of work with different levels of uncertainty. Standard equipment may be well defined. Building or civil work may be well understood. Integration with existing systems may be genuinely uncertain. Using one pricing method for everything looks tidy but can misallocate risk: either the supplier prices large contingencies on the uncertain parts, or the buyer carries open-ended risk on parts that could have been fixed.
A coherent approach applies one set of objectives and governance across the project but allows different pricing methods where the work genuinely differs. Consistency belongs in how the project is governed, not necessarily in every commercial term.
Staging: pricing uncertainty as it falls
Staging is often the most practical answer for work that is uncertain now but will become clearer after investigation. The first stage, such as a site survey, design, prototype or investigation of existing equipment, is paid on rates or a modest fixed fee. Its purpose is to reduce uncertainty. Once it is complete, the main stage can be fixed-priced with much smaller contingency, or priced by another method if uncertainty remains.
Staging has costs. It adds a step, and the buyer may feel committed to the stage-one supplier. Address this by stating at the start whether the stage-one supplier will be invited to price the main stage, whether other suppliers may also price it, and who owns the results of the investigation. The estimating project costs from cost drivers article describes the supplier’s version of this approach, a paid discovery phase.
If you are the supplier
Small suppliers are often asked for fixed prices on work they cannot fully define. Some practical responses:
- State your assumptions and exclusions clearly, so the buyer knows what the price covers.
- Offer a staged approach: a paid investigation or design stage, then a fixed price for the main work.
- Use provisional sums for genuinely undefined items, with a clear explanation of how they will be adjusted.
- Separate the certain from the uncertain: a fixed price for defined work and rates for the rest.
- Price the contingency honestly if you must give a single fixed price, and explain what it covers.
Buyers usually prefer an honest explanation of uncertainty to a low price that turns into variations later.
A worked example
This is an illustration. A manufacturer wants a supplier to design, build and commission an automated cell that will link to an existing filler and palletiser. The delivery model is clear: the supplier will be responsible for design, integration and commissioning against a performance requirement. The pricing method is less clear.
The owner first asks three integrators for a fixed price for the whole job. The quotes are $640,000, $720,000 and $910,000. The lowest excludes all work on existing equipment. The spread and the exclusions suggest the interfaces with the existing equipment are not well understood.
The owner changes approach:
- Stage 1: a paid investigation and design stage on time and materials, capped at $45,000, to survey the existing filler and palletiser and complete the design.
- Stage 2, equipment and installation: fixed price once the design is complete.
- Stage 2, integration with existing equipment: target cost, with overruns and savings shared equally between the business and the integrator.
Stage 1 costs $41,500 and finds that the palletiser’s controls need replacing, which none of the original quotes had included. It estimates the excluded interface work at roughly $170,000 to $190,000. The integrator then prices the equipment and installation at a fixed $585,000 and agrees an integration target of $180,000.
The integration actually costs $196,000, an overrun of $16,000. Under the equal sharing formula, the business pays $180,000 plus half the overrun, which is $8,000, for a total of $188,000, and the integrator absorbs the other $8,000.
| Item | Cost |
|---|---|
| Stage 1 investigation and design | $41,500 |
| Equipment and installation (fixed) | $585,000 |
| Integration (target cost after sharing) | $188,000 |
| Total | $814,500 |
The total is higher than the lowest original quote, but that quote excluded work the investigation showed was needed. Adding the estimated excluded work to it gives roughly $810,000 to $830,000, before any dispute about what was included. The main difference is not the total. It is that the uncertainty was resolved before the main commitment, rather than argued over during delivery, and that both parties had a reason to control the cost of the uncertain integration work.
How this applies to a small Australian business
Small businesses both buy and sell under these pricing methods. Practical steps:
- Decide the delivery model first, then the pricing method.
- Ask whether the work meets the conditions for fixed price: definition, competition, repeatability, low change, supplier capacity.
- Read a wide spread of quotes as a warning that the scope may not be well defined.
- Use different methods for different parts where uncertainty differs.
- Consider staging for work that becomes clearer after investigation.
- Make sure you can administer whatever method you choose.
- As a supplier, state assumptions and exclusions and offer staged or mixed pricing for uncertain work.
- Check state rules on allowances in residential building, and take advice for significant contracts.
The how much design before seeking quotes article covers how to prepare the requirement before asking for prices.
Signals worth watching
- “Fixed price” used as if it describes the whole arrangement.
- Wide spreads between quotes for the same scope.
- Long lists of exclusions attached to low quotes.
- Many variations on fixed-price work.
- Time-and-materials or cost-plus work with nobody checking costs.
- Suppliers declining to quote because the risk is too great.
- Arguments about what a fixed price included.
Common mistakes
- Choosing the pricing method before the delivery model.
- Assuming fixed price transfers all risk.
- Using one method for every part of a project.
- Fixing a price before the work is defined.
- Choosing an open-book method without the capacity to oversee it.
- Setting a target cost without a sound basis.
- Ignoring the contingency suppliers include for transferred risk.
Frequently asked questions
Is fixed price always cheaper for the buyer? No. For well-defined work, competition often makes it good value. For uncertain work, suppliers include contingencies and variations tend to follow, so the final cost can be higher than under another method.
How do we set a fair target cost? Base it on a defined scope and a transparent estimate, ideally after an investigation or design stage. Some buyers ask an independent estimator to check it. Agree how actual cost will be measured before work starts.
What sharing ratio should a target-cost arrangement use? There is no standard answer. Equal sharing is simple and common in discussion, but the ratio should reflect how much each party can influence the cost. Many arrangements also cap the buyer’s share of overruns. Take advice on the detail.
Can a small business use open-book pricing? Yes, if it can review the records. For small jobs, a simple open-book arrangement with a cap and regular review of timesheets and invoices can work well.
What if the supplier insists on fixed price for uncertain work? Ask what contingency is included and what is excluded. Consider whether staging or separating the uncertain parts would give better value. Sometimes paying for certainty is the right choice, as long as it is made knowingly.
How should variations be handled under a fixed price? Agree a simple, written process before work starts: how changes are requested, how they are priced, who can approve them and that no varied work proceeds without written approval.
Questions to ask
- Have we decided the delivery model separately from the pricing method?
- Who owns design and integration, and does the pricing method fit that?
- Which uncertainties can suppliers price credibly, and which should we keep?
- Does this work meet the conditions for a fixed price?
- Are we choosing fixed price because it fits or because it is familiar?
- Can we administer the method we are choosing?
- Would staging reduce uncertainty before the main commitment?
Bringing it together
Delivery model and pricing method are separate decisions. Decide who designs, builds and integrates first, then choose a pricing method that shares cost uncertainty in a way the work can support and the business can administer. Fixed price is efficient when the work is defined, repeatable and unlikely to change. When it is not, staging, mixed methods or shared-risk pricing may give better value. The aim is not to avoid fixed price, but to know when its simplicity is real and when it is only hiding uncertainty that will surface later.
Source: KEVOS notes, drawing on teaching material distinguishing delivery models from contract pricing types and on the continuing preference for lump-sum fixed-price contracting. Examples and figures in this article are illustrations. This article is general information, not legal or financial advice.
