Money is a difficult concept for your child to learn. The main stumbling block is that we expect him/her to understand that one object (a coin or a note) actually represents more than one of something.
From the beginning of your child's maths journey we are always very careful to emphasise one to one correspondence, for example, in counting but when it comes to money all that gets turned on its head. All of a sudden, without any warning, your child is presented with one coin but is told this might look like one but in fact it means 2, or 5 etc.
Your child may find this idea difficult to grasp and need lots of support and practical experiences in order to fully understand the concept. However, once fully understood, this concept becomes easy for your child as he/she will use money on a daily basis