Can I do work before hearing Havdala after Shabbat?
Can I do work before hearing Havdala or before reciting the evening service?
One may not do work before Havdala. However, one who recited Havdala in the evening prayers may do work. Also, it is enough to say 'Baruch hamavdil bein kodesh lechol’ to permit doing work before hearing Havdalah (Shulchan Aruch and Rema Orach Chaim 299:10. Chazon Ovadia on Shabbat Part II Page 273).