How do you adjust prior year taxable benefits for T4?

Hi there, 

Welcome to the QuickBooks Community. I'll be happy to share more info so you're on the right track with accomplishing your QuickBooks goals. 

In order to adjust a prior year T4 I recommend contacting our support team outside of the Community. A specialist will be able to share your screen and assist you further. Here are our contact details below: 

• Schedule a Callback or start a Chat: click (?)Help in the upper right in QuickBooks Online > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.
• Social Media: Facebook, Twitter, and Instagram.
• Support hours are from Monday to Friday between 9 a.m. and 8 p.m. ET.

Feel free to keep me posted on how you make out. I'll be one message away in case you need anything else.