As stated above, but wanted to add that you are allowed to keep £20 a week csa money without it affecting your income support, all the rest above goes back to the government. Eg.. csa you get £45 , you get to keep £20 = £25 left, government will take the £25.
You can either get full income support & let the csa just send you the £20 once they recieve it from the dad, OR you can keep the full csa but your income support will be reduced.
Personal experience i would keep the full income support, As if the dad doesn't pay csa one week you will be very stuck. Then if you get csa its a bonus.