26 U.S.C. § 63 — Taxable income defined

(a) General rule: Except as subsection (b) says otherwise, 'taxable income' means gross income minus the deductions this chapter allows — but not counting the standard deduction. (b) Individuals who don't itemize: If a person chooses not to itemize deductions for the year, their taxable income is instead their adjusted gross income minus: the standard deduction; the personal-exemption deduction under section 151; any deduction under the pass-through business-income section 199A; the deduction under section 170(p); the deduction under section 224; the deduction under section 225; and the part of the home-mortgage-interest deduction under section 163(a) that comes from the exception in section 163(h)(4)(A). (c) Standard deduction: The standard deduction is the basic standard deduction plus the additional standard deduction. The basic standard deduction is: 200% of the 'other case' dollar amount below, for a married couple filing jointly or a surviving spouse; $4,400 for a head of household; or $3,000 for anyone else. (Special post-2017 rules below raise the last two figures.) The additional standard deduction is the sum of the extra amounts a taxpayer qualifies for under subsection (f), for being 65 or older or blind. Starting with tax years after 1988, several of these dollar figures — the head-of-household and 'other case' amounts, and the paragraph (5) dependent-limit amounts — go up each year using a cost-of-living formula, with different base years for different amounts. There's a special cap for a dependent: if someone else can claim this person as a dependent, that person's basic standard deduction can't be more than the larger of $500, or $250 plus the person's own earned income. Some people get no standard deduction at all (it's zero): a married person filing separately when their spouse itemizes; a nonresident alien; someone filing a short tax year because they changed their accounting period; or an estate, trust, common trust fund, or partnership. For tax years starting after 2017, the standard deduction is increased: the head-of-household figure becomes $23,625 and the 'other case' figure becomes $15,750, and the normal cost-of-living rule stops applying to those two figures. Instead, starting in tax years after 2025, those two dollar amounts get their own inflation increase, calculated using 2024 as the base year and rounded down to the nearest $50. (d) Itemized deductions: 'Itemized deductions' means all deductions this chapter allows, except the ones used to figure adjusted gross income, and except any deduction already listed in subsection (b). (e) Election to itemize: A taxpayer only gets itemized deductions if they elect to itemize for the year — otherwise none are allowed. (Whether a deduction is normally 'allowable' is judged without regard to this election rule.) The election is made on the tax return, in whatever manner the Secretary prescribes. A taxpayer can change their election after filing, under Treasury regulations — but if their spouse filed a separate return for the matching year, the change is only allowed if the spouse also changes their election consistently, and both spouses agree in writing to let the IRS assess any resulting tax deficiency even past the usual deadline. This change rule doesn't apply if the spouse's tax liability for that year was already settled through an IRS compromise under section 7122. (f) Aged or blind additional amounts: A taxpayer gets an extra $600 for being 65 or older by year's end, and another extra $600 for a spouse who is 65 or older (if the taxpayer can claim an exemption for that spouse). A taxpayer gets an extra $600 for being blind at year's end, and another extra $600 for a blind spouse (same exemption condition) — if the spouse dies during the year, blindness is judged as of the date of death. For someone who is unmarried and not a surviving spouse, these $600 figures become $750 instead. 'Blind' means central vision no better than 20/200 in the better eye with glasses, or a visual field so narrow that its widest angle is 20 degrees or less, even with better visual acuity. (g) Marital status: For this whole section, marital status is determined under section 7703.