# Cost-plus billing

Source: https://contracko.com/glossary/cost-plus-billing

# Cost-plus billing

Billing based on actual costs incurred plus an agreed margin, rather than a fixed price.

## Definition

Under cost-plus billing the supplier invoices the actual cost of labour, materials and subcontractors plus an agreed fee or percentage margin. It shifts cost-overrun risk to the client and is suited to work whose scope cannot be defined in advance. Cost-plus arrangements usually require open-book accounting and audit rights so the client can verify the underlying costs.

## Example

> A renovation of unknown scope is invoiced on a cost-plus basis at actual hours times the rate card plus a 10% overhead fee.

## Why this is a business risk

Cost-plus contracts give suppliers little incentive to control costs, since every additional cost increases the base on which the margin is applied. Without strong audit rights and reporting requirements, clients can face runaway invoices with limited ability to challenge them. For suppliers, failing to track actual costs accurately exposes them to disputes about what was properly incurred.

## How to manage it

- Define which costs are reimbursable and which are included in the overhead fee, to prevent disputes about what falls inside or outside the base.
- Require the supplier to submit detailed cost breakdowns with each invoice, supported by timesheets, receipts or subcontractor invoices.
- Set a budget cap or target cost so the client has a cost ceiling even if the contract is technically open-ended.
- Include audit rights allowing the client to verify cost records within a defined period after each billing cycle.
- Review total spend at agreed milestones and consider converting to a fixed price once the scope becomes sufficiently defined.

### How Contracko helps

Contracko extracts billing terms, audit rights and cost-cap provisions from cost-plus contracts and tracks them alongside spend milestones. Teams can set reminders for invoice review windows and audit deadlines, reducing the risk that cost overruns go unchallenged.

## Relevant for

[Construction](https://contracko.com/industries/construction-industry)[Engineering & Architecture](https://contracko.com/industries/engineering)[Consulting](https://contracko.com/industries/consulting)

## Related clauses

- [Payment Terms Clause](https://contracko.com/clause-library/payment-terms)
- [Audit Rights Clause](https://contracko.com/clause-library/audit)

## Related terms

- [Fixed price vs. cost-plus](https://contracko.com/glossary/fixed-price-vs-cost-plus)
- [Open-book contracting](https://contracko.com/glossary/open-book-contracting)
- [Audit right](https://contracko.com/glossary/audit-right)
- [Change orders (variations)](https://contracko.com/glossary/change-orders)

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## Frequently asked questions

Common questions about this term.

- **Q:** What costs are typically excluded from a cost-plus base?
  **A:** General overhead, profit margin, financing costs and penalties are usually excluded from the reimbursable base and instead covered by the agreed fee. The contract should list exclusions explicitly.

- **Q:** How is the margin or fee structure in a cost-plus contract typically expressed?
  **A:** Either as a fixed fee (a set amount per deliverable or period) or as a percentage of reimbursable costs. A fixed fee is preferable as it removes the incentive to inflate the cost base.

- **Q:** What is open-book accounting in a cost-plus context?
  **A:** Open-book accounting requires the supplier to give the client full access to the cost records underpinning each invoice, including subcontractor invoices, payroll records and material costs. It is a key control mechanism in cost-plus arrangements.

- **Q:** Can a cost-plus contract include a guaranteed maximum price?
  **A:** Yes. A guaranteed maximum price (GMP) cap means the client pays actual costs up to the cap, after which the supplier absorbs any overrun. It is a common hybrid between pure cost-plus and fixed price.

- **Q:** How do disputes about cost-plus invoices typically arise?
  **A:** The most common disputes concern whether a cost was properly incurred, whether it falls within the agreed reimbursable scope, and whether the rate or allocation basis is correct. Clear definitions and regular invoice review reduce these disputes significantly.

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