How can I upgrade my quickbooks plan while I have already paid for a lower plan? Will it charge me the full price?

The discounted rate is not applicable when upgrading or downgrading your plan. You have to click the Buy button and open a new blank account to get the discounted rate.

https:// quickbooks.grsm.io/us-promo

https:// quickbooks.grsm.io/us-promo-6months