You cannot install more than one TurboTax desktop CD/Download personal tax editions for the same tax year on a computer.
Why are you using more than one TurboTax desktop CD/Download edition?
The desktop programs can complete as many tax returns as needed without charge after initial purchase. Each program includes 5 free federal tax return e-files (number set by IRS rules). Any further tax returns can be printed and mailed. You can install as many different state programs as needed using the desktop editions. But can only e-file up to three states with one federal tax return. Any further state returns have to be printed and mailed.
