You can pay into one Junior ISA of each type (Cash or Stocks & Shares) per tax year for your child, and the annual contribution limit of £9,000 is shared between your child’s JISAs. For example, you could pay £5,000 into a Cash JISA and £4,000 into a Stocks & Shares JISA for your child in the same tax year.
The £9,000 contribution limit is per child - meaning if you have multiple children, they each will have an allowance of £9,000 per tax year.
Contributions you make into a Junior ISA do not count towards your own £20,000 annual ISA allowance.