Addressing a baronet, or a knight, is very simple but few people seem to be able to get it right. This is possibly the fault of those who design computer programs who only allow sufficient spaces for Mr, Mrs, Ms, Rev and Dr followed by initials and surnames.
A baronet is entitled to the prefix “Sir” and the word “Baronet” after his name and this precedes any other post-nominal letters to which he might be entitled. The word “Baronet” is usually shortened to “Bt” or “Bart”, the latter being slightly old fashioned and not often used nowadays.
In writing, a baronet should be addressed on an envelope as “Sir John Jones Bt” and NEVER as “Sir Jones”, “Sir J Jones” or “Sir Bart”. If the baronet is entitled to post nominal letters the correct address would be “Sir John Jones Bt CBE”. If the baronet has a military or clerical title this would come first and the correct address would be “Colonel Sir John Jones Bt CBE or “The Rev Sir John Jones Bt CBE”. Titles emanating from sources other than the Sovereign, such as “Professor”, “Doctor” or “Alderman”, are not normally used in conjunction with the style of a baronet or knight. The letter should begin “Dear Sir John,”. Verbally a baronet or knight should be addressed by, or referred to, by his first name as “Sir John” and NEVER as “Sir Jones”.
Certain Scottish baronets combine their names with a territorial designation such as Sir Ronald Lindsay of Dowhill Bt and should be addressed as such in writing. Verbally this baronet should be addressed as “Sir Ronald” in the same way as other baronets.
The wife of a baronet or a knight has the style of “Lady” before her surname. Unless she is the daughter of an Earl, or higher, in the Peerage she would be styled “Lady Jones” and not “Lady Belinda Jones”. However to avoid confusion with others with the same surname she may, in correspondence, be styled “Lady (Belinda) Jones” or “Belinda, Lady Jones”.
Upon her husband’s death the widow of a baronet retains her title as “Lady Jones” unless the new baronet is married when she must choose to become either “Belinda, Lady Jones” or the “Dowager Lady Jones”, the former style being the more usual. Should she remarry, she takes her style from her husband. A divorced wife of a baronet takes the style “Belinda, Lady Jones” until such time as she remarries