Base date: definition and example
A contractual reference date used for specified adjustments or risk allocation.
By Jack Butler-Kettle · Updated
Guidance for England and Wales. Check the contract, amendments and facts that apply to your job.
What it means in practice
A base date is a contractual reference point. Depending on the form and clauses, it may be relevant to price adjustment, tax or changes in law. It is not necessarily the tender date, signature date or start date, and it does not create a right to an uplift by itself.
Read the date alongside the mechanism that uses it. Price rise loss prevention can help identify where your terms leave cost movements with your business.
Worked example
The facts
A subcontract permits a specified material adjustment measured from a stated base date.
What happens
The subcontractor checks the agreed index and the relevant baseline value.
It applies only the categories and periods allowed by that clause.
What this shows
The contractual reference date supports the calculation; a general increase in supplier prices is not enough on its own.