Forcing 1NT

Unpassed 1♠-1NT is forcing to accommodate strong invitations, especially 6+♥, which is one step away from 4♥.

1♠-1NT-Usually 7–11, 0–3♠
2♣NF, 4+♣ or BAL MIN
2♦NF, 4+♦
2♥NF, 4+♥
2♠MIN, 6+♠
2NTBAL MAX
3♣♦♥MAX, 5+#
3♠MAX, 6+♠