The first most important thing to consider is partnership agreement. There are quite a few different ways this bid can be handled. This is what I would teach my novices. 1NT - 4D (Transfer) I would expect the 4D bidder to have 9 to 11 HCP and 6 hearts with more or less he would do a regular transfer of 2D with less and 6 heasrts , inviting with 3H (Opener should have at least 2) Opener with a maximum value hand may decide to go to game with more, respond with either a control card at the 4 level, or bid 4 Hearts at the four level. If opener has 16+ opener can entertain a query.