Set a current allowance to specify the amount of money allowed to spend on any downloads (games, apps, and more).
Billing purchases from the Play Store or App Store to your T-Mobile account is blocked while Family Allowances is active. You can still use a credit card or prepaid card to purchase from these stores.
One important call-out, though, is that these settings only work while connected to the T-Mobile network. Family Allowances settings don't work over Wi-Fi (or on Wi-Fi calling, for the call setting options).