A postnuptial agreement, or “postnup,” is similar to a prenuptial agreement, except this legal contract is written and signed after the couple is legally wed. A postnup sets forth how assets will be divided, and may include other provisions dictating marital conduct like the division of household chores to monogamy expectations to how frequently in-laws may visit. Like a prenup, a postnup an be a powerful estate planning tool, when used properly.

While most people believe that postnups are only useful for the rich (which they are), there are many circumstances in which couple of modest means should consider drawing up a postnup.

1. You have children from a prior relationship

Postnups can pre-determine the share of assets your spouse will receive in the event of a divorce or your death, and can ensure that your children will receive the inheritance that you designate for them. Without a postnup, many states automatically give the current spouse a share of your estate upon your death.

2. You or your spouse owns a business.

A postnup can also protect the income or assets you earn during the marriage. This is crucial for spouses who own their own companies. Without a postnup, an ex-spouse may be entitled to collect a percentage of the business or its earnings.

3. You recently received a large inheritance.

If one of you receives a sizable bequest or gift from a family member, you may want to consider a postnup. Under normal circumstances, new assets can easily become joint assets. A postnup can help keep the new inheritance earmarked for you in case of a marital split.