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Young couple cohabitating

How to Prove Cohabitation in Illinois: All You Need to Know

According to a study by the Pew Research Center, the percentage of cohabitation has increased. Throughout the years, it has become more and more common for couples to cohabitate before getting married or even having wedding plans at all. The study showed that 59% of young adults have lived with their partners without marrying them.

What Is Cohabitation?

Cohabitation is the case of a couple living together without being married. The concept may vary between states. Some states don’t include same-gender couples who live together under the cohabitating concept.

States like Illinois, don’t entirely accept cohabitation. In case the couple cohabitating splits, the rules of property division will not apply to them since they do not have a husband-and-wife relationship. Having a valid cohabitation agreement may help the case and simplify all legal matters if the couple splits.

Cohabitation may involve legal and financial implications that should be considered. A family law attorney can assist you in creating an agreement concerning financial obligations, including rent, utility bills, and debt. This agreement will also outline the responsibilities of each parent if there are children involved. Moreover, if you have unresolved obligations with a prior relationship, you could be subject to legal repercussions.

What happens if you are divorced or in the process of divorcing, and you start cohabitating with your new partner? What happens to your child custody, and how it affects your child support case?

Youg adults cohabitating

Terminating Spousal Support Due to Cohabitation

Divorce is not as simple as signing a legal document. This legal process leads to various sets of agreements, child support, legal responsibilities, and other support obligations, all within family law.

One of the primary responsibilities is alimony or spousal support, commonly known in Illinois as maintenance. Even though each state has its legal actions regarding alimony, Illinois’ spousal maintenance laws are very clear.

According to LegalMatch, a few factors can help determine the amount of alimony for each case in Illinois. Some of them are the spouse’s age, length of the marriage, present and future earning ability of both parties, and presence of domestic violence.

Maintenance orders contain specific terms of when the spousal support payments are no longer necessary when they can be modified, and if they can be modified at all.

Divorcenet published an article that mentions details on how to modify alimony. To obtain a new alimony order, a significant change of circumstances needs to be shown. Some evidence that can help you modify it is:

  • Proof of decreased income or loss of a job
  • If the spouse stopped working due to an illness
  • If the supported spouse has experienced an increase in income.

In Illinois, spousal maintenance obligations end either:

  • automatically based on a date specified in the court order;
  • automatically upon remarriage;
  • when the recipient spouse begins cohabitating with a significant other, which requires the payor-spouse to ask the court;
  • automatically upon death unless a life insurance policy is to be paid to the recipient ex-spouse when the paying ex-spouse dies;
  • upon petition where there is a substantial change in circumstances; or
  • by voluntary agreement, but the judge may not agree.

So, termination of maintenance can be requested when the maintenance recipient cohabitates with a significant other. However, spousal maintenance does not end automatically with cohabitation, as it does with remarriage. The ex-spouse paying spousal maintenance must go to court and prove that the ex-spouse receiving maintenance is, in fact, living with another person in a marriage-like relationship.

Free Download: Questions to Aid in Determining Cohabitation

This free list is not an exhaustive or definitive list. However, answering these questions fully and accurately may help your legal counsel better understand the relationship and the possibility of qualifying as a de facto marriage.

For example, if you are divorced and receiving spousal support, but you start living with your new partner, the ex-spouse can file a motion to terminate maintenance payments. In some states, cohabitating is reason enough for your ex-spouse to stop paying alimony. In others, the judge needs evidence that cohabitating has helped you financially and you no longer need your ex-spouse to pay future maintenance. 

Under the statute, 750 ILCS 5/510(c), the obligation to pay maintenance terminates if the recipient ex-spouse is cohabitating with another person “on a resident, continuing, conjugal basis.” See In re Marriage of Susan, 367 Ill. App. 3d 926 (2d Dist. 2006); In re Marriage of Sappington, 106 Ill.2d 456 (1985). It is the responsibility of the payor ex-spouse to show that the recipient ex-spouse is involved in a de facto marriage.

Cohabitation Agreement

How Does Cohabitation Affect Child Support?

When it comes to the matter of the petition to change the spousal maintenance or child support order, the same rules apply to both.

The truth is that child support orders cannot be modified just by proving that one of the spouses is living with a new partner in a marriage-like relationship. The spouse cohabitating must have experienced a substantial financial change to have the order modified.

Due to how child support is calculated, sometimes it is hard to prove that because of cohabitation, there has been a substantial change. If you are interested in calculating child support payments, please visit

The non-parent spouse or partner is not legally obliged to contribute to child support. Though, it may be considered since it affects the economic prospects of the parent involved.

Child support will always be a legal responsibility for both parents. The only way cohabitation may affect child support is by increasing or decreasing the amount of support given.

When it comes to child custody, each case is different, and the outcome depends on various factors the judge has to take into consideration.

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Factors Considered to Establish Cohabitation

Proving cohabitation is not just helpful for child support cases but also for cases such as alimony obligations and even terminating alimony. 

Factors that the judge may use in court to define the relationship status as a cohabitation:

  • Length of the relationship
  • Amount of time the couple spends together
  • Type of activities they attend together
  • The interrelation of their personal affairs
  • If they spend vacations together
  • If they spend the holidays together

Furthermore, the court in In re Marriage of Weisbruch, 304 Ill. App. 3d 504 (2d Dist. 1999) considered some different factors outlined below since this was a same-sex couple situation and way before Illinois adopted same-sex marriage:

  • Buying a home and titling it in joint tenancy;
  • Dividing household expenses;
  • Sharing a joint account;
  • Co-signed loans for each other;
  • Listed as co-owners on their cars;
  • Named in each other’s wills;
  • Were the primary beneficiaries of each other’s life insurance policies;
  • Sharing a bedroom;
  • Taking vacations together; and
  • Sending out joint Christmas cards.
House going through a divorce

This case-based analysis is more on the “financial implications of the relationship” since they were “most relevant to determining the need for maintenance, not the presence or absence of sex.” Id at 105.

Judges take into consideration the above-mentioned factors to determine whether or not to terminate the alimony due to cohabitation.

It is difficult to list all facts that can help cases with evidence of cohabitation due to the uniqueness of each case. The burden of proof relies on the one who pays spousal support. This could change depending on the case. Remember that each individual case presents different circumstances.

Evidence that Can Prove Cohabitation

Proving that the supported party is cohabitating is more complicated than proving that the partner has remarried. There needs to be evidence of a de facto relationship presented to the court for modification or termination of alimony. By court orders, sexual relationships don’t need to be proven. Nonetheless, it needs to be more than that your ex-spouse is living with another person.

Some of the evidence that has been used in previous cases are:

  • Photographic (photo or video) evidence with the parties involved entering the place of residence and staying overnight.
  • Documentation, such as magazine subscriptions, credit card statements, joint household bills, and other legal documents that show the couple has the same address.
  • Legal papers or any type of document that shows the couple shares a title or leases property jointly.
  • Information gathered from social media accounts showing they are a couple.
  • Any type of evidence that the couple shares bank accounts.
  • Photographs of the couple spending holidays together or on vacation.
  • Evidence that neither of the parties involved has other residences.

Since each state has its alimony laws, you can’t determine your case based on California law, for example. This is one of the main reasons why hiring a professional in your state is crucial to your case.

Evidence to prove cohabitation

How to Prove Cohabitation in an Alimony Case?

Hiring a private investigator to gather evidence for your case is almost vital. Not only will they obtain all the information that would be almost impossible for you to extract, but they will also provide you with useful information for the court.

Since each case is unique, there isn’t a standard list of evidence that could be submitted.

Professional private investigators will not only conduct surveillance, but they will also research public records, review social media accounts, and even examine their garbage for evidence if necessary.

Evidence presented by private investigators that have been useful for terminating alimony cases goes from jointly titled properties to verifying that neither of the parties involved has another residence. There are various valuable pieces of information that only a private investigator with the proper tools can gather.

Hiring a private investigator that helps you legally get the proof you need to support your case is the best solution. A private investigator can implement their professional training and all of their tools to gather the case information needed legitimately without harming the case. 

Post Update: The article was updated on January 20th, 2023, originally published on June 25th, 2020. It has been completely revamped and updated for accuracy and comprehensiveness.

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Free Download: Questions to Aid in Determining Cohabitation

This free list is not an exhaustive or definitive list. However, answering these questions fully and accurately may help your legal counsel better understand the relationship and the possibility of qualifying as a de facto marriage.