When do you use Mrs or Ms if divorced or widowed?

Use "Mrs." for a divorced or widowed woman who chooses to retain her ex-husband's last name or her late husband's name. "Ms." is appropriate for a divorced or widowed woman who prefers not to disclose her marital status or wishes to be addressed without reference to her former marriage. Ultimately, the choice depends on personal preference, so it’s best to ask the individual which title they prefer.