When the invitation says “Formal or Black Tie Optional” or can also have several other aliases, such as “Black Tie Suggested” this means you are free to go either with long gown or cocktail dress in slightly less formal than black tie. The options for ladies include a long dress, dressy separates, or a formal cocktail dress.
Actually, if you receive an invite with the term black tie optional know that it mostly applies slightly less pressure for the men to wear a tuxedo (a dark navy or black suit, and crisp white shirt, with a dark, or neutral tie is appropriate here). So generally, a tuxedo isn’t required, but the event is still formal enough for one to be appropriate.
Not only guests are required to wear outfit that is formal enough for black tie, but I also think “black tie optional” implies formal gowns that are simpler, less glamour than those that are fully embellished. This can include floor length gown that comes in modern designs such as with cut-out, full skirt, or fun color block, but with less details, appliques or embellishments.
Check out some suggestions below, and be free to opt for a cocktail dress in modern style, even you can opt for a little black dress or little white dress as long as the dress comes in festive and party look – but still not too bridal-y
ASOS : Crop Top Maxi WIth Embellishment ($171) / Jarlo Tall Caden Lace Detail ($162) / Coast Christelle Maxi Dress ($313) / Virgos Lounge Greta Off Shoulder ($215) House Of Fraser : Coast Adelina Maxi Dress (£180) / Biba Wrap Button Detail Maxi Dress (£149) / Coast Tyler Maxi (£195) / Coast Leta Maxi Dress (£220)
Phase Eight : Dotty Tapework (£179) / Harmony Tape Dress (£125) / Carmen Tapework Dress (£95) / Emma Embellished Dress (£65)
Net A Porter : Dion Lee One-shoulder Metallic Knitted Dress (£645) / Karla Spetic Sereia Ruffled Organza-paneled Silk-satin Dress (£475) / Halston Heritage Tulle-trimmed Sequined Stretch-jersey Dress (£460) / Dion Lee Draped Crepe Midi Dress (£450)
If you want to wear an LBD, since formal or black tie weddings usually suggest the bride to wear a full-skirted bridal gown, technically you are safe to wear LWD as long as your dress doesn’t outshine the bride – avoid materials like tulle or lace, or silhouette and details that usually come in a wedding dress such as embroideries, beads, etc. But for a safe bet when wearing LBD or LWD, learn “Wedding Guest Attire: What to Wear to a Wedding (Part 1)”