It is not cheating. If you are still employed - you fulfill job requirements you agreed on in exchange for money. If you are not fulfilling these requirements a

It is not cheating. If you are still employed - you fulfill job requirements you agreed on in exchange for money. If you are not fulfilling these requirements any company fill just fire you. Side projects are irrelevant. (Unless it is specifically said in contract and you are being paid for a chance of inventing for company something forth extra pay)