In the QuickBooks Online section, select Upgrade your plan.
Review the available plans and then select Choose plan.
Follow the on-screen steps to upgrade your plan.
If you've already done these steps or if the Advanced option is unavailable, contact our QuickBooks Support Team. They should be able to take over and assist you with upgrading the subscription.
Drop a comment below if you're unable to reach out to our support or if you need further help with the downgrade process. I'll be happy to help you some more.
QBO Advanced is only available for US region at the moment. One said they will release for CA region within this year. No info for UK or other regions.