To see your prior true-up charges for prior years, you would bring up your past statements to see them. Your estimated True Up shows on your bill monthly. After eleven months of minimum charges, you will be able to see your final true-up bill for that year on your statement.
To find and/or download a copy of your old bills, sign in to Your Account. Look under the Your Account header and click the Bill & Payments History link to access the last six months. To access up to 24 months of bills and payments, use the scroll bar on the right-hand side of the module, and scroll down to the bottom to select the link for "View up to 24 months of activity" expander. Note: you may need to click in the module for the scroll bar to appear.