1. to establish a "genuine material factor" defence in an equal pay case the employer must show that the variation between the woman's contract and the man's contract is not tainted with sex. If the employer cannot show that the reason was not due to the difference of sex, he must show objective justification for the disparity between the woman's contract and the man's contract and also show that it is a current factor which is still relevant and is not merely historic.

2. market forces are capable of being a "genuine material factor" justifying a differential in pay, even when adversely affecting women, provided the market does not operate on sexist principles. If the whole of the pay differential cannot be justified by the need to pay market rates an employer can rely on such differential as justified by that need. It is for the employer to show that some differential is justified by market forces and also to satisfy a Tribunal what that differential is.

3. the aim of improving productivity by payment of bonuses can be a "genuine material factor" defence but an employer must monitor it rigorously. The means must be proportionate to the aim and it cannot be proportionate to pay bonuses to achieve a legitimate objective when that objective is not being realised.

4. an express "equality clause" can only bite where a comparator's contract either has a term of a similar kind to that in a claimant's contract, or where there is a corresponding term that can be transposed.

For relevant general notes see Sex discrimination/equal pay and terms of employment/genuine material factor defence .