Answer by
LeheckaG (1826)
Business-formal-attire for (U.S.)men:
(white) long-sleeve(possibly short-sleeve in summer/warmer-climates) dress-shirt
(often with button-down-collar);
(black/blue/brown/grey) business-suitcoat, optional-matching-vest,
& matching dress-pants/slacks/trousers;
matching-belt or suspenders;
an appropriate-conservative (not too bold/large/small) tie (optional-clasp);
appropriate-underwear;
dark-colored (black/blue/brown/gray matching-suit) socks;
polished dress-shoes;
Similar for women,
but often a conservative-dress/skirt & nylon-pantyhose (instead of pants/slacks/trousers & socks).