Requirements Specification (Lastenheft)
Document created by the client that defines what a project or product must achieve and why, ideally in verifiable, measurable requirements.
A requirements specification, known in German as Lastenheft, is drawn up by the client before a project is awarded. It describes the requirements from a usage perspective: what a product, system, or service must deliver and for what purpose. The technical implementation, the how, is deliberately left open for suppliers to propose.
In the project workflow, the requirements specification forms the basis for tendering. Suppliers calculate their bids against it, and the client can compare offers objectively because every bidder is responding to the same set of requirements. Without a clean requirements specification, bids drift apart in scope and become hard to compare.
To serve its purpose, requirements should be as concrete and measurable as possible, for example expressed through figures, tolerances, or testable criteria rather than vague statements of intent. Loose or incomplete requirements specifications tend to cause misunderstandings, change requests, and disputes over the agreed scope later on.
Practical Example
A workshop wants to procure a new coating line and states in its requirements specification: throughput of at least 40 parts per hour, colour changeover under three minutes, integration with the existing ERP system, and compliance with current emission limits. Three equipment builders then submit comparable offers based on this.
How Leanshift Helps
A precise requirements specification is a small piece of process work in itself: it forces you to think through your own needs clearly before investing. That habit of clarifying requirements before starting is part of continuously improving processes and organisation.
Frequently Asked Questions
Who writes the requirements specification?
The client, since only the client fully knows its own needs and goals.
How does it differ from the functional specification?
The requirements specification covers the what and why from the client's perspective; the functional specification answers with the how from the supplier's perspective.
Is a requirements specification legally binding?
It usually becomes part of the contract as an attached scope description, even though it is not, by itself, a standalone contract.