A couple separates in August, signs a decree in November, and asks you in March which return to file. Marital status on December 31 decides almost everything that follows.
Filing status sets the standard deduction, the brackets and the credits a taxpayer gets. After a marriage or divorce, the filing status for the whole year turns on the taxpayer's status on December 31. A divorce decree final on December 30 makes the taxpayer unmarried for the entire year, and a marriage on December 31 makes them married for the entire year.
Four situations decide whether a marriage still counts on December 31:
- Legal separation: A taxpayer with a decree of divorce or separate maintenance by year end is unmarried. A separation agreement without a decree leaves the couple married.
- Common-law marriage: Some states recognize common-law marriage, where a couple is married without a license or ceremony.
- Death of a spouse: A surviving spouse may file a joint return for the year the other spouse died, as long as the survivor did not remarry before year end.
Common mistakes
- Using the decree date instead of December 31. A decree dated December 30, 2025 makes both parties unmarried for all of 2025. Candidates often split the year into married and unmarried months. There is no proration.
- Filing Form 8379 for a deficiency. Injured spouse relief only recovers a refund that was offset. A $16,778 assessment caused by a spouse's omitted income is a liability problem, so it needs Form 8857, not Form 8379.
- Deducting post-2018 alimony. A 2021 decree ordering $2,000 a month produces no deduction for the payer and no income for the recipient. Only instruments executed on or before December 31, 2018 keep the old rule, where the payer deducts and the recipient includes.
Bottom line
- Marital status on December 31 fixes filing status for the entire year; there is no proration for a mid-year divorce.
- MFJ 2025 standard deduction is $31,500, MFS $15,750, HOH $23,625; if one MFS spouse itemizes, the other's standard deduction is zero.
- MFJ carries joint and several liability for the whole tax; MFS and HOH do not.
- Abandoned-spouse HOH needs all five prongs, including the spouse out of the home for the entire last six months.
Exam shortcut
Read the stem for the injury first. If the words are "refund," "offset," "past-due child support" or "student loan," the answer is Form 8379, and the tax on the return is correct. If the words are "deficiency," "understated," "omitted income" or "did not know," the answer is Form 8857. For alimony, find the instrument date before reading anything else. 2018 or earlier equals deduct and include.
The full lesson (about 3,832 words, 26 min read) adds 2 worked examples, all 6 common mistakes, a self-check, free in the app.
Learning objectives
- 1
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