Scheme members pay contributions at the rate of 11% of pay. Pay in this context means your basic pay - it does not include overtime or any other allowances you receive.
You get tax relief on your contributions, which means that for every £1 you contribute your net pay is only reduced by 78p.
The Police Authority makes it's contribution to the Scheme by making up the shortfall between contributions paid in to the Scheme and benefits paid out of the Scheme.
If you are unable to achieve the maximum Scheme benefit by the time you reach retirement age, you can pay up to a further 4% of pay to boost your benefits.