You can absolutely use your married name, despite a lack of name change, in your business: e.g. in terms of naming your business, in terms of how you introduce yourself to people, what's on your business card, how you market or advertise, etc.You would still need to use your legal name (maiden name) on tax returns, on business filings (e.g. incorporating), and on other legal documents (e.g. contracts, though there you might indicate that  you also go by the married name).