Punz

Hi I was wondering if someone can help, this is the first time ever I am doing this self-assessment, my salary is 55k. and I got child benefits of 1820 for the whole year, when i am completing the form it says I owe 4-5k i don't understand why the amount is so much higher then child benefits and i paid all my taxes in my paycheck. I have now stopped the child benefit has its stressing me out.