Some parents agree between them how much to pay for their children's upkeep. If you need help either you or your partner can seek advice from a solicitor or apply to the Child Support Agency (CSA) for a decision on the amount of maintenance that should be made. The CSA will also make sure the payments are made.
Some parents agree that one of them will continue to meet specific expenses, such as school fees, holidays, premiums on insurance policies or payments into savings accounts set up for the children. If you can't agree, a court will sometimes make orders to provide for things like school fees and larger items of expenditure.
For more details of the sort of provision that can be made, see If you have children.