Common-law marriages create all sorts of headaches for governments and courts. In its simplest form, a common-law marriage is a marriage that can arise in some jurisdictions without having been registered with the government. Because these marriages are unregistered, someone (either a judge or bureaucrat) must determine on a case-by-case basis whether two people are actually married when they attempt to file a joint tax return, seek to have a tax-free inheritance, look to adopt a child, attempt to establish the paternity of a child, seek health insurance through the spouse’s employer, and in many other contexts. These determinations consume a significant amount of government resources, and therefore governments dislike them.
As of the date of this post, common-law marriage exists in only nine states (plus Washington D.C.). Illinois is not one of them.
If you so desire, you can still be deemed to have a common-law marriage in nine states, Alabama, Colorado, Kansas, Montana, Rhode Island, South Carolina, Texas, and Utah, and the District of Columbia. There is a dispute as to whether common-law marriage still exists in Oklahoma, and common-law marriage only exists in New Hampshire for purposes of distributing property at the death of one spouse. In all other states, including Illinois, you cannot obtain a common-law marriage and must apply for a marriage license if you desire to be married.
The Full Faith and Credit Clause (art. IV, sec. I of the US Constitution) requires the individual states to recognize the “public acts, records, and judicial proceedings of every other state.” If you became common-law married in a state that recognizes common-law marriage, Illinois must recognize your marriage.
Long-term cohabitation is dangerous for significant others in Illinois who sacrifice their career for the relationship.
If you want the benefits of marriage in Illinois, you need to get married.
Courts award spousal support (occasionally called “alimony”) to divorcing spouses who sacrificed their career and education to maintain the marital home. There is no such thing as spousal support, alimony, or “palimony” for unmarried persons. Illinois courts have flatly refused to recognize palimony since 1978, explaining that “it is not appropriate for this court to grant legal status to a private arrangement substituting for the institution of marriage sanctioned by this State.” See Hewitt v. Hewitt, 77 Ill.2d 49, 394 N.E.2d 1204 (Ill. 1979).