[barsikb]

My partner made 1NT direct overcall after 1H opening. I have a weak hand, long Diamonds and don't want partner to play NT. What is my bid please?

Do many players bid System On after partners 1NT overcall these days? If using system-on, does that include Minor Suit transfers (4-way transfers)?

[blackshoe]

It depends on your agreements. If you play system on, also known as 'front of card', and the system described on the front of your card (i.e., after a 1NT opening by partner and a pass by RHO) includes minor suit transfers, then minor suit transfers are on after your partner overcalls 1NT and your RHO passes. I think 'system on' is pretty common — I play it with most of my partners — but I don't have hard data on that.

[barsikb]

System on would solve a problem here. If playing 4WT, which bid to use for transfer to Diamonds? I learned 2S for Clubs, 2NT for Diamonds which makes things complicated about hands which would be bid 2NT natural. I read somewhere about 3C as transfer to 3D. Is it a good way to bid?

[blackshoe]

Playing 2NT as a transfer to diamonds, you go through Stayman if you want to bid 2NT naturally. It's not all that complicated.

I suppose you can play 2NT as natural and 3♣ as a transfer to diamonds if you want. It means giving up whatever meaning you had for 3♣ before the change, though.