Hello This is a situation that came up recently. My partner opened 1NT (16-18). RHO overcalled 2D, and I bid 2H, intended as a transfer to spades. P did not treat it as a transfer, so I did a little research, and found that in Standard American, systems are OFF after opps interfere. We transfer only to the majors. The way I would play it is systems are ON. Here is my reasoning: Case 1: 1 NT – (2C)-?; Easy. Club bid will not affect the transfer bids, so transfers are on. Case 2: 1 NT – (2 D)- ? : Also easy. Double is transfer to H, and 2H –> 2 S. Case 3: 1 NT – (2 H)- ? : X is transfer to Spades. The transfer to Hearts is out, but so what? Opps outrank you! Case 4: 1 NT – ( 2 S or higher): Transfers are automatically off. The advantage to having systems always on, IMHO, is it’s easy to remember as long as you have discussed X for “stolen” bids, and you retain the advantage of some transfers, if not all, being available. In other words Systems always ON when P bids a strong NT. Are there any disadvantages? Any discussion? Comments ?