Formerly and formally are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Formerly (pronounced “fohr-murr-lee”) is an adverb. It means a previous state for someone or something. Examples include an old brand name, a previous job, or a surname. Formerly is often used to modify “known.” For example, for period in the 1990s, Prince was referred to as TAFKAP, or The Artist Formerly Known As Prince, in print media.
Formally (pronounced “fohr-mah-lee”) is an adverb. It means objects and behaviors associated with an elite, refined, high-caliber setting. Red carpet events demand its attendees dress formally.
The following story uses both words correctly:
Forde Fordham, formerly Fisk Ficus, wasn’t informed that he needed to dress formally to attend tonight’s event. Fortunately, his wingman, Gage Garrison, tipped him off at the last second, and he ducked into a tux rental store before he arrived.