The dress code is the most frequently misunderstood instruction a guest will receive, and the most frequently abused. Not because guests are careless, but because the terms themselves have been diluted by misuse until they mean almost nothing. Let us restore their meaning.
White tie is the most formal dress code in Western etiquette. For men: a tailcoat, white piqué waistcoat, white wing-collared shirt, white bow tie, and black patent shoes. For women: a full-length evening gown, long gloves optional, and jewellery that is not daytime. White tie is rare at weddings. If you issue it, you must mean it, and you must be prepared for the fact that many of your male guests will not own a tailcoat and will need to hire one. Do not issue white tie as a flourish. It is a requirement.
Black tie is the standard formal evening dress code. For men: a dinner jacket (tuxedo), black or midnight blue, with a black silk bow tie, a white dress shirt, and black patent or well-polished Oxford shoes. For women: a floor-length gown or a sophisticated cocktail dress, at the wearer's discretion. Black tie is the dress code of the formal evening wedding. It is widely understood and widely available. If your evening wedding is formal, this is the code to issue.
Black tie optional, sometimes called black tie invited, is a concession. It tells male guests that black tie is preferred but that a dark suit is acceptable. In practice, it means half your male guests will wear dinner jackets and half will wear dark suits, and the photographs will reflect the split. If uniformity matters to you, issue black tie. If it does not, issue black tie optional. Do not issue it and then complain about the result.
Cocktail attire is less formal than black tie. For men: a dark suit, shirt, and tie. For women: a cocktail dress, typically knee-length or slightly longer, or an elegant separates ensemble. Cocktail attire is appropriate for an afternoon or early-evening wedding that is formal but not black-tie. It is the most flexible of the formal codes and the one most guests will get right without instruction.
Lounge suit, sometimes called business formal, is the standard for daytime formal weddings. For men: a suit and tie, any colour appropriate to the season. For women: a day dress, a skirt suit, or a tailored trouser ensemble, with a hat or fascinator if the culture and venue permit. Lounge suit is the default for a British daytime wedding and should not be confused with cocktail attire, which is more formal.
Creative black tie is a genuine category, though a recent one. It permits a black-tie foundation with a degree of personal expression — a coloured dinner jacket, a patterned bow tie, a statement accessory. It is not a licence for fancy dress. The foundation remains black tie. The creativity is in the detail, not the structure. Issue it only if your guests have the style to carry it.
And finally, the codes that are not codes. "Festive" means nothing and will produce a room of conflicting interpretations. "Dressy casual" is a contradiction in terms. "Smart casual" is a workplace instruction, not a wedding one. "Come as you are" is an insult to the occasion. If you cannot name the dress code, do not invent one. State the formality of the event — "formal," "semi-formal," "informal" — and trust your guests to dress accordingly. They will.