Contra proferentem is a rule of construction applying to written documents or deeds. The rule provides that if the wording of an agreement is ambiguous or uncertain, but not otherwise, the contract should be construed more strongly against the person whose words they are rather than the other party.
In the case of John Lee & Son (Grantham) Ltd v Railway Executive (1949) it was found that:
'We are presented with two alternative readings of this document and the reading which one should adopt is to be determined, amongst other things, by a consideration of the fact that the defendants put forward the document. They have put forward a clause which is by no means free from obscurity and have contended... that it has a remarkably, if not extravagantly, wide scope and I think that the rule contra proferentem should be applied’
If a party has incorporated its own standard terms and conditions of trade into an agreement then in the event of ambiguity those terms and conditions will be construed contra proferentem that party. Where however the parties execute standard form contracts, the contra proferentem rule will only operate in respect of amendments or additions to the contract.
Contra proferentem is a particularly important rule of construction in relation to exclusion clauses.
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