What is included in maintenance payments

Mark5555555555

Good morning, I want to start making payments towards my children's upkeep. I currently have a 50 / 50 residency order but the 2 teenagers have asked about living with mum. My question is do I include my gross salary, included in my gross is a yearly bonus that fluctuates and a monthly vehicle allowance, I am unsure what I include to use for the calculation, any help would be greatly appreciated 

Comms69

Generally you would use whatever your last p60 said.

As it's a voluntary agreement, you can simply make a reasonable offer.