Dress codes at the top end are quieter than they used to be, but they have not disappeared — they have gone unwritten. Reading them correctly is part of hosting well. The safe principle: at a business dinner it is better to be marginally overdressed than underdressed, because the cost of the first is nothing and the cost of the second is a signal you did not intend to send.
Decode the common labels
"Smart casual" means a collared shirt and good shoes, jacket optional but welcome — no trainers, no shorts. "Business casual" leans a touch sharper: a blazer reads correctly. "Jacket required" means exactly that, and the better rooms that say it will lend you one rather than turn you away. "Formal" or "black tie" is now rare in restaurants outside specific events, and will be stated explicitly.
Read the room, the city and the hour
Codes shift by geography and time. A Parisian or New York grande-dame room runs more formal than a Nordic or Australian one of the same calibre; dinner is dressier than lunch. When in doubt, a well-cut jacket is the universal solvent — it clears almost every bar and is easy to remove if the room is relaxed.
When you are the host
Tell your guests the code in advance if it is at all strict — "they ask for a jacket" is a kindness, not a fuss. It spares your guest the doorway embarrassment and confirms, once again, that you had thought of them.
Check before you go
Each restaurant page on this site notes the room's formality where it matters, and a one-line call to confirm a jacket policy is never wasted before an important dinner.