Last year I used Deluxe. I will sell stock this yr, will Dlx handle this or do I need to upgrade to Prem?If I purchase Pro, can I upgrade later by paying the difference?

For the Online web browser version you need Premier to enter investments.  Yes you can upgrade if you need to.  What is Pro?

If you buy the Desktop CD/Download program then you can use Deluxe.  All the Desktop programs have the same forms. You just get more help and guidance in the higher versions.