If your child has a master account this is a breach of the SEN Terms of Service. This is because a new account cannot be created without agreeing to provide accurate information, including date of birth. If your child is under 18 and has a master account they could have only created it by providing an incorrect date of birth.
If your child has a master account they will be able to add card details to the account and make purchases by using the card to add wallet funds. They will also be able to access all PlayStation Network services and interact with other PlayStation Network users without restriction.
We will not refund any purchases that were made on the master account, in line with the Store Cancellation Policy but the new sub account can be linked to a new local user on the same PlayStation 4 and PlayStation 3 as the master account's local user. This means that downloaded content can be shared across both accounts (subject to any PEGI/BBFC ratings or parental controls on the PlayStation systems). This option is not available on PS Vita, PS TV or PSP as these systems only allow one local user account.
You need to have your own master account registered to an accessible email address, whether you use PlayStation Network or not, to ensure you have full visibility of any purchases and the ability to limit purchases made by your child:
This is to ensure your child cannot add funds to an account wallet or alter the parental controls. Make sure of the following before you allow your child to use your PlayStation 4 or PlayStation 3 system (click any point about account or console settings that you are unsure of to go to full instructions):
The monthly spending limit is set at zero when you create a sub account. If you want to allow your child to make purchases from PlayStation Store the spending limit allows your child to spend up to a certain amount every month (unspent funds do not roll over).
Your child can only spend funds already in the master account wallet. If the wallet does not have sufficient funds, your credit/debit card will not be charged, even if the monthly spending limit should allow the purchase.