As per my knowledge limited liability partnership is having different legal status so there will never be a case of  filing retun twice 

REASON:the is partnership  firm and LLP are having diffrent legal status as per income tax and other laws also

ramcharan can u give some instances from the law enacted for the same

 I can not give pratical example but i can let you know by giving an imagination

If a partnership firm is coverted into company then how we treat the company as diff entity that is the same case that we need to treat the LLp