These rules come from the official Royal Enclosure Dress Code document published by Ascot Racecourse, verified in August 2026; they apply to the Royal Enclosure, as the source does not detail the other enclosures. For women, a hat is mandatory. A headpiece or hatinator is accepted only if its base measures at least 10 cm in diameter, and fascinators are banned, except for guests under 17. Dress straps must be at least 2.5 cm wide; strapless, one-shoulder, off-the-shoulder, open-back halterneck and spaghetti-strap dresses and tops are prohibited, as are sheer fabrics.
For men, the black, grey or navy morning coat comes with a mandatory black or grey top hat. It may only be removed in a restaurant, a private box, an enclosed outdoor seating area, a terrace, a balcony or a garden. Any customization of the top hat (colored ribbons, feathers, ornaments) is prohibited. The classic trap is therefore twofold: a headpiece with a base under 10 cm, or straps that are too narrow, is enough to put an outfit out of compliance.