I took this following quote from an article I found some years ago which I kept because it inspires the strict expectations which black tie on the invite invokes.
I have read this article very carefully and at all black tie events the jacket is to remain worn until late, or in the case of the UK armed forces they are given permission to remove jackets.
As the wearer of one of our fancy back shirts no infringement to this dress code stated below has occurred. As the evening relaxes the venue warms up and conversation between guests become easier you tend to find jackets are removed, at this point everyone is still the same with their white shirts, except the wearer of the Fancy back shirt with his inspired patterned back and sleeves. All attention will be given to him it will get him noticed and will be a great conversation starter when approaching other guests. So what is stopping you? “Putting a bit of fun into formal”.
Quote from an article.
“Black Tie”, “Black Tie Required”
The appearance of Black Tie on an invitation indicates unequivocally that the host expects tuxedos to be worn. Black Tie required or Black Tie only means the same thing but can come across as heavy-handed. Hosts should avoid the latter unless they are certain that there will be guests too naïve or inconsiderate to infer the mandatory nature of the former.
There will likely be those few guests who will wrongly interpret Black Tie to simply mean "formal" and arrive in whatever they feel appropriately dressy. A gracious host will excuse the appearance of the uninformed among them, viewing the transgression as a valuable learning experience for these guests. As for the wilfully inconsiderate, the host’s congeniality need last only as long as the evening.
Wear proper black tie or send your regrets. It’s that simple.
Hosts and organizers do not specify this dress code because they want you showing up in a black suit. Rather, they have put a tremendous amount of effort into making the evening exceptional and are relying on you to respect the unique elegance and traditional uniformity that black tie so brilliantly imparts. Yet there always seem to be those men who feel the party is all about them and they can dress as they please. “Some guys,” observed The National Post, “especially younger fellows who feel they’re really successful, take pride in flouting dress codes and showing up in business suits, often not dark, and without a tie . . . Perhaps kids think it’s too much trouble to rent or buy a black tie. Grow up or don’t show up.”