Obsolete buildings clause

A clause used in property insurance policies when insured buildings are old or not ideally suited to current occupation. Partial losses are dealt with on a conventional reinstatement basis but total loss (or major damage) by rebuilding using modern materials and design. The sum insured reflects this.

Occupational deafness

See Noise-induced hearing loss.

Occurrence basis

Same as Losses-occurring basis.

Onus of proof

The obligation that rests on one party to a contract to demonstrate that a state of affairs exists or that the promissory terms of a contract have been triggered. In a contract of insurance the burden of proof falls on the insured to demonstrate that a valid claim exists and to quantify the claim: if the insurer wishes to invoke an exclusion or exception, the insurer has the burden of proving that the terms of the exclusion or exception apply.

Operative clauses

The part of an insurance policy that sets out the contingencies covered by the policy.