For tax purposes, when is a written separation agreement required?

Suppose a husband and wife have informally separated. The spouses do not have a court order or a written agreement or anything. One spouse then begins paying the other money he or she considers alimony and hopes to claim it as a tax deduction. The I.R.S. will not accept this.

A written separation agreement is necessary if the spouses making payments of support of the other during this separation wants to claim a tax deduction for these payments. By the way, payments of support such as this are not uncommon, and are often called "separate maintenance" or "alimony pendente lite" (essentially, "alimony until the litigation").

Basically, the I.R.S. needs something more than the spouses’ say so in order to properly allocate deductions and income. Even if a divorce decree states that certain payments are alimony, the I.R.S. need not accept a court’s characterization. For its purposes, the I.R.S. Code and associated rules are controlling. Spouses, however, can agree in a separation instrument or a court-imposed order what payments or portions of payments would not be considered alimony.

The court order will serve the same function for the IRS as a written agreement would.