# Fixed price vs. cost-plus

Source: https://contracko.com/glossary/fixed-price-vs-cost-plus

# Fixed price vs. cost-plus

The choice between a guaranteed fixed contract price and billing of actual costs plus a margin.

## Definition

Fixed-price contracts give the client cost certainty and place overrun risk on the supplier, whereas cost-plus contracts pass actual costs through to the client with an agreed margin. The choice depends on how well the scope can be defined: well-specified work suits fixed price, while uncertain or evolving scope suits cost-plus. Hybrid models such as target-cost or guaranteed-maximum-price contracts blend the two.

## Example

> A software build with a stable specification is contracted fixed-price, while the discovery phase is billed cost-plus.

## Why this is a business risk

Choosing the wrong pricing model for the work creates structural misalignment. A fixed price on an ill-defined scope incentivises the supplier to minimise effort and generate change orders, eroding the cost certainty the client thought they had. A cost-plus model on well-defined work removes supplier cost discipline and inflates the client's bill. Both errors increase the risk of disputes and cost overruns.

## How to manage it

- Assess scope clarity before choosing the pricing model: use fixed price only when the deliverables, quality standards and timeline can be fully specified.
- Consider a phased approach: cost-plus for initial discovery or design, then fixed price once the scope is defined.
- Build change-order controls into fixed-price contracts so that scope changes are priced and approved before work starts.
- For cost-plus, set a target cost or guaranteed maximum price to give the client a financial ceiling and the supplier an incentive to stay within it.
- Document the basis for the pricing model choice in the procurement file to support governance and audit reviews.

### How Contracko helps

Contracko's AI review identifies the pricing model used in uploaded contracts and flags key terms such as change-order rights, cost caps and audit provisions. This gives procurement and finance teams a quick overview of where cost certainty exists across a portfolio and where cost exposure remains open.

## Relevant for

[Construction](https://contracko.com/industries/construction-industry)[Software Development Agencies](https://contracko.com/industries/software-development)[Engineering & Architecture](https://contracko.com/industries/engineering)

## Related clauses

- [Payment Terms Clause](https://contracko.com/clause-library/payment-terms)
- [Change Order (Variations) Clause](https://contracko.com/clause-library/change-order)

## Related terms

- [Cost-plus billing](https://contracko.com/glossary/cost-plus-billing)
- [Total Cost of Ownership](https://contracko.com/glossary/total-cost-of-ownership)
- [Open-book contracting](https://contracko.com/glossary/open-book-contracting)
- [Change orders (variations)](https://contracko.com/glossary/change-orders)

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## Frequently asked questions

Common questions about this term.

- **Q:** Which pricing model is better for the buyer?
  **A:** It depends on scope certainty. Fixed price protects the buyer when the scope is clear. Cost-plus protects the buyer from a supplier padding the price for risk when scope is genuinely uncertain.

- **Q:** Can a contract combine fixed price and cost-plus elements?
  **A:** Yes. Hybrid models are common: a fixed lump sum for the defined core scope, with cost-plus for variations, or a guaranteed maximum price that blends certainty with flexibility on final cost allocation.

- **Q:** How does the pricing model affect liability caps?
  **A:** Liability caps in fixed-price contracts are typically set as a multiple of the contract price. In cost-plus contracts the cap may be harder to calculate since the final contract value is not known upfront; parties often tie it to estimated or actual fees paid.

- **Q:** Is fixed price or cost-plus more common in public procurement?
  **A:** Fixed price is preferred in public procurement because it provides transparency and cost certainty. Cost-plus is used for complex or research-based contracts where the scope cannot be defined, but it requires strong audit provisions to satisfy public accountability requirements.

- **Q:** What triggers the conversion from cost-plus to fixed price in a phased contract?
  **A:** Typically the completion of a defined design or discovery phase that produces enough specification detail for the supplier to price the remaining work reliably. The conversion should be documented in a contract amendment.

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