Normally, each partner in an unmarried couple keeps his or her own last name. It’s easy, legal, and creates few, if any, practical problems. Occasionally, however, members of an unmarried couple want to use the same last name—his name, her name, a hyphenated version of the two names, or a completely new name for both.

This can be done with little difficulty, as it’s fairly simple to change your last name by getting a court order.

Bear in mind that you cannot change your name to defraud creditors, for any illegal purpose, to benefit economically by the use of another person’s name, or to invade someone’s privacy (don’t name yourself Madonna or Bill Clinton). Also, you can’t take on a name that is likely to incite violence (such as a racial epithet) or is inherently confusing (such as a string of numbers). Otherwise, you can change your name for any reason and assume any name you wish.

Change of Name by Usage

In some states, it is legal to change your name by simply using a new name and gradually changing your official documents to match the name you are using. However,we do not recommend the usage method of changing your name, even if you live in a state that allows it. Most government agencies will no longer just take your word for the fact that you’ve changed your name, but will require a court order with a judge’s signature. And you don’t want to run afoul of the Patriot Act or any other new “homeland security” rules by having documentation in two different names. It’s far better to just spend the few hundred dollars and take the time to change your name legally through the court petition method.

Change of Name by Court Order

The second way to change your name is by court order. Getting a court order is usually pretty simple: You fill out, and file at the courthouse, a short petition, publish legal notice of your intention to change your name in a local legal newspaper, and attend a routine court hearing.

Once you obtain the court order changing your name, you must still change your records, identity cards, and documents. All you need to do is show the various bureaucrats the judge’s order.

Each state has its own laws governing the court order method, so check your state laws for details. How to Change Your Name in California, by Lisa Sedano and Emily Doskow (Nolo), will help you do the job quickly and efficiently in that state.

Legal Repercussions of Changing Your Name

In some states, using the same last name can show intent to establish a common law marriage. If your state recognizes common law marriage and you use the same last name, you may create an implication that you intend to be married—especially if you tell others that you are married. If you live in a common law marriage state and want to use the same name, but don’t want to be married, it’s a good idea to sign a brief Agreement of Joint Intent Not to Have a Common Law Marriage. Also, don’t hold yourselves out to family and friends as a married couple.

Also, using the same last name combined with other factors, such as a claim by one of you that you orally agreed to pool income, may imply that you intend to share your earnings and property. If you wish to keep all property separate but share your last name, it’s an extremely good idea to sign an agreement to keep your property separate.