The singer shared a photo from the set of the promo this weekend using the hashtag #workbitch, which had been the rumoured title of her comeback song.
"Hot day on set... ;) A little dirty, little flirty, danced my ASS off. Stoked for tomorrow!" Spears tweeted following the shoot.
The new track is said to sample RuPaul's 1992 hit 'Supermodel (You Better Work)'.
Spears is due to appear on Good Morning America on September 17, where she is expected to make a big announcement.
Her publicist told Digital Spy: "Britney has been using a vocal coach and going to regular sessions and has also been working hard with her choreographer in preparation for what's coming up.
"With album eight on its way and a rumoured Las Vegas residency in the pipeline, eagle-eyed fans have spotted that all of Britney's social networks have adopted a blacked-out theme... the mystery continues!"