Can I do my son's taxes on my computer if he has his own on-line account?

[Anonymous]

if he gives you permission and the details to access his a/c. 

or are you asking about uing desktop software? 

[SUZNB57]

Sure you should still be able to.  That is why they have the checks at the end before you e-file to verify information & ensure a return for that person for that year has not been submitted yet.