How is non statutory redundancy calculated?

I was hoping if someone could help me out with the calculation of non statutory redundancy. Is this calulated from your P60 or from your pay slip? I know that the two figures can differ when you take into account pension payments and the like. Is this part totally at the discretion of the company involved? Thank you in advance

It's totally discretionary.

Companies have no obligations to pay anything other then statutory so if they pay more, it is probably up to each company to decide how they do so

Ask management what they are basing their calculation on.

Also is it a big company? There are rules that govern large scale redundancies, and terms and criteria are more than likely negotiated with the Unions. Speak to a Union official if there is one there.

Ok, but in this case a figure was agreed in writing but payroll have paid a different amount as they say the amount agreed in principle was calculated incorrectly. But this figure was set out as the final figure against which the redundancy was agreed. What are the implications here? Are the company obliged to pay the full amount?