When a child user turns 18 years of age, the account is eligible to upgrade to an adult PlayStation® Network Account, this is not required, however. You cannot revert back to a child account.
Benefits of Upgrading to an Adult PlayStation® Network Account
They control their own account.
Keeps their own Online ID, trophies and Friends List.
Carry over all games, videos, music, and services.
Fund their own wallet and purchase power.
How to Upgrade
On the Date the Child Turns 18 Years of Age
Upon turning 18 years old, when the Child Family Member next logs in with their PSN account, they will be asked if they want to upgrade their account to an Adult Family Member. Follow the in system steps to upgrade to an Adult Family Member.
Upgrade After the System Request
If you clicked "Do This Later," when first prompted in the system, you can still upgrade by following these steps:
Step 1: Go to Settings, select Account Management
Step 2: Select Account Information, then Upgrade Your Account
Step 3: You will be asked to verify you want to upgrade your account. Click "Continue" and follow the onscreen instructions.