You can never DQ an opponent before five rounds have passed. Before then, you can only cancel the match, which will lead to neither side getting anything from the battle.
Also, unless your opponent explicitly tells you that it is fine to DQ, or the DQ limit is stricitly enforced, you should wait at least two weeks before DQing an opponent. Also, you should always attempt to contact your opponent beforehands, too. This is not a rule, but it is a polite gesture.