How do I withdraw my child from a tournament?

You can withdraw from My Panel while entries are still open. After that the organiser has to do it.

The short answer

You can do this yourself only while entries for that tournament are still open.

Once entries have closed, the page will refuse, and you have to ask the organiser instead.

If the category was full, withdrawing frees your place and the first player on the waiting list takes it.

Sign in and open My Panel.
Find the entry you want to withdraw.
You can only withdraw entries for your own players, or for a child you are the guardian of.
Choose to withdraw, and confirm.

Write to the organiser and ask them to withdraw the entry. The draw may already be made, so tell them as early as you can.

The organiser collects the fee directly, so any refund is their decision. Ask them.

Withdrawing a doubles entry withdraws the pair. Tell your partner, because the entry was theirs as well.