If I understood your question rightly, we should say "after completing".

after <sb> completes <something> "After I complete this test, I'll be finished." after completing <something> "After completing the test, you will be finished" [The pronoun in the second, subordinate clause is assumed in the first clause] after <something> is completed "After the test is completed, you will be done." "After the road is completed, traffic should be better"