Domicile is the place where a person or entity has its primary, permanent home or principal place of business. Domicile is important in the law for determining the state and county in which a person or entity may be sued, vote, and is obligated to pay taxes. For a person with multiple homes or different places of residence, domicile is the place the person plans to return to after being away, and may be indicated by the place where the person maintains important services and relationships, such as banking, driver’s license registration, incorporation, and work/employment. A person or entity is said to be a domiciliary of the domicile.

In Massachusetts, domicile is defined as the place where an individual has their true, fixed, and permanent home and principal establishment, and to which they intend to return whenever absent. It is the location with which a person has the most settled and permanent connection, and is often evidenced by where they vote, pay personal income taxes, and have their driver's license and vehicle registration. For entities such as corporations, domicile is typically where the entity is incorporated or where its principal place of business is located. Establishing domicile affects legal rights and obligations, including jurisdiction for lawsuits, tax liability, and eligibility for state services. For individuals with multiple residences, determining domicile involves evaluating factors such as time spent in each location, the location of family and personal belongings, and where one intends to return. Changing one's domicile requires both physical presence in the new location and the intent to remain there indefinitely.