Taxpayer information and filing requirements

Taxpayer biographical information, age, and filing status

A taxpayer’s biographical information (name, age, marital status) and information about dependents are used to verify the identity of the taxpayer and related dependents. It is also helpful to have a copy of the taxpayer’s prior year tax return for consistency of tax information and knowledge of recent correspondence from the Internal Revenue Service to discover probable omission of tax information that may benefit the taxpayer.

What the prior-year return supplies. Several 2025 entries come from the 2024 return:

• Carryovers: a capital loss (2024 Schedule D), unallowed passive losses (Form 8582), charitable contributions over the AGI limits (usable for the next 5 years), a net operating loss (deducted on Schedule 1, line 8a), and the minimum tax credit (2024 Form 8801, line 26).
• IRA basis: generally line 14 of the last Form 8606 filed.
• Payments: a 2024 overpayment applied to 2025 estimated tax, included on Form 1040, line 26.
• 2024 Schedule A: a state or local income tax refund received in 2025 is taxable only if the taxpayer itemized in 2024 and deducted state income taxes, and only to the extent the deduction lowered the 2024 tax.
• 2024 tax and AGI: they set the estimated tax safe harbor (100% of 2024 tax, or 110% if 2024 AGI was over $150,000, or $75,000 if married filing separately).
• E-file signature: a Self-Select PIN signature is validated with AGI from the originally filed 2024 return (not an amended return or an IRS math-error correction), unless last year’s PIN or an IP PIN is entered.

U.S. citizens or residents of the United States must file a return based on three factors: age, gross income, and filing status. The age of an individual taxpayer determines whether he/she qualifies for additional deductions, retirement distributions, credits, etc. The amount of a taxpayer’s gross income determines whether or not a taxpayer is required to file a return - the threshold generally matches the standard deduction for the taxpayer’s filing status (for 2025: $15,750 single, $31,500 married filing jointly, $23,625 head of household), except that a married taxpayer filing separately must file with gross income of just $5, and it’s higher once the taxpayer turns 65. The married filing jointly status often increases the beneficial dollar limits for deductions and credits. A preparer must also confirm the taxpayer’s immigration status and citizenship during intake, since these affect which forms and worldwide-income rules apply. Additionally, questions regarding possession of digital assets and Marketplace health insurance must be answered as part of the work to prepare a tax return, including reconciling any advance Marketplace subsidy on Form 8962 using Form 1095-A. See Form 1095a and Form 8962.

If a taxpayer is an alien, then he/she is considered a nonresident alien unless he/she meets either the green card test or the substantial presence test for the calendar year. If a taxpayer does not meet either of these tests, then he/she may be able to choose to be treated as a U.S. resident for part of the year (dual-status aliens). This usually occurs in the year of arrival in or departure from the United States. A resident alien for tax purposes is a foreign national (not a U.S. citizen) who meets either the green card or substantial presence test as described in IRS Publication 519.

Green card test. An alien who is a lawful permanent resident (holds Form I-551) at any time during 2025 is a resident for 2025. The status lasts until it is taken away or is determined to have been abandoned. If the taxpayer doesn’t also meet the substantial presence test, residency starts on the first day of the year the taxpayer is in the United States as a lawful permanent resident, so someone who first gets a green card partway through the year is a dual-status alien for that year.

Substantial presence test. An alien is a resident for 2025 if physically present in the United States on at least 31 days in 2025 and at least 183 days counting all the days in 2025, 1/3 of the days in 2024, and 1/6 of the days in 2023. Presence for any part of a day counts as a full day, but days as an exempt individual don’t count (“exempt” refers to counting days, not to tax): a foreign government-related individual on an A or G visa (other than A-3 or G-5), a teacher or trainee on a J or Q visa (generally not if already exempt for any part of 2 of the 6 preceding years), a student on an F, J, M, or Q visa (generally for no more than 5 calendar years), or a professional athlete competing in a charitable sports event. Exempt students, teachers, trainees, and athletes file Form 8843 to exclude their days.

Example: Counting days

Hana was physically present in the United States on 120 days in each of 2023, 2024, and 2025. Is she a resident for 2025 under the substantial presence test?

Answer: No. She counts 120 days for 2025, 40 for 2024 (1/3 of 120), and 20 for 2023 (1/6 of 120), a total of 180, short of 183.

Nonresidents and their spouses. A nonresident alien who is engaged in a U.S. trade or business, or whose other U.S.-source income wasn’t fully taxed through withholding, files Form 1040-NR. Interest on U.S. bank deposits that isn’t connected with a U.S. trade or business is excluded from a nonresident alien’s income, so it doesn’t by itself require a return. The 2025 return is due April 15, 2026, if the nonresident had wages subject to withholding, and June 15, 2026, otherwise. A nonresident alien generally can’t file jointly, but a U.S. citizen or resident married to one at year-end can elect to treat the spouse as a resident for the entire year by filing a joint return with a statement signed by both spouses. Both are then taxed on worldwide income, and neither can claim under a treaty to be a nonresident. The election carries over to later years (joint or separate returns) until it is revoked or otherwise ended, and once ended it can’t be made again.

IRC §61 stipulates that gross income is all income from whatever source derived, whether received in cash, services, or property; United States citizens and resident aliens are taxed on their worldwide income unless it is specified as nontaxable. Generally, nonresident aliens are taxed only on U.S.-source income.

Individual taxpayer identification number (ITIN)

An ITIN is issued to resident and nonresident aliens (including spouses and dependents) who need a taxpayer identification number but are not eligible for a Social Security Number (SSN). An ITIN is requested on Form W-7, which generally must be submitted with the federal tax return the number is needed for. An ITIN not used on a federal return at least once for 2022, 2023, or 2024 expired on December 31, 2025, and must be renewed on Form W-7 before it is used on a 2025 return. An ITIN is for tax purposes only, and a filer using one can’t claim the earned income credit. The number of days present in the U.S. affects residency status for tax purposes. An Employer Identification Number (EIN) is used for business entities, estates, and trusts. U.S. citizens and residents use an SSN (a resident alien who isn’t eligible for an SSN uses an ITIN), or an Adoption Taxpayer Identification Number (ATIN) in the limited case where a child has been placed in the taxpayer’s home for legal adoption and the adopting parent can’t obtain the child’s SSN in time to file (requested on Form W-7A). Separately, a taxpayer with foreign financial accounts may need to file an FBAR (FinCEN Form 114, filed with FinCEN once accounts total more than $10,000 at any time in the year) and/or Form 8938 (attached to Form 1040, with higher thresholds that depend on filing status and residency) - meeting one requirement does not excuse the other; International information reporting compares the two.

An Identity Protection PIN (IP PIN) is a six-digit number, known only to the taxpayer and the IRS, that prevents anyone else from filing a return with the taxpayer’s SSN or ITIN. Anyone with an SSN or ITIN who can verify their identity may opt in, and the IRS also assigns IP PINs to confirmed victims of tax-related identity theft. An IP PIN is valid for one calendar year, and a new one is generated each year. It is entered in the Identity Protection PIN box next to the signature on Form 1040 (a separate box for a spouse who has one). A missing or incorrect IP PIN causes an e-filed return to be rejected and a paper return to be delayed until the IRS can verify it.

Prior IRS correspondence. Earlier notices can change the return being prepared:

• CP2000: income or payment information from third parties, such as employers or financial institutions, didn’t match the return. It proposes changes and isn’t a bill; the taxpayer replies by the date shown, and one who agrees and has nothing else to report doesn’t amend. The omitted income belongs on the current return, and other years with the same omission should be amended.
• Math-error notice (such as CP11): the IRS corrected a mathematical or clerical error and assessed the tax without a notice of deficiency. Within 60 days after the notice, the taxpayer can request abatement, which the IRS must grant, reassessing only through deficiency procedures (IRC §6213(b)).
• Identity verification letter (5071C series): a return filed under the taxpayer’s SSN or ITIN is held until the taxpayer verifies their identity, using that return and a prior-year return.
• Credit reduced or disallowed: if the EIC, CTC/ACTC, ODC, or AOTC was reduced or disallowed for any reason other than a math or clerical error, Form 8862 must be attached the next time the credit is claimed. The credit is barred for 2 years after a final determination that the claim was due to reckless or intentional disregard of the rules, and for 10 years after one of fraud.

Filing status is generally determined by whether you are married or unmarried on the last day of the tax year.

Definitions

Single

Unmarried, divorced, or legally separated by the end of the tax year.

Married filing jointly

Filing with your spouse or same-sex spouse on the same tax return, even if your spouse has deceased during the tax year.

Married filing separately

Married filing separate tax returns for the same tax year.

Head of household

Unmarried or considered unmarried on the last day of the tax year, who paid more than half the cost of keeping up a home for the tax year, and who had a qualifying person (a qualifying child, or a relative the taxpayer can claim as a dependent - not someone who is a dependent only because they lived with the taxpayer all year as a household member) live with them in that home for more than half the year - a dependent parent does not have to live with the taxpayer to qualify.

Qualifying surviving spouse
Can use this status for 2 years following the year of your spouse’s death and must meet 4 requirements.

1. You were entitled to file a joint return with your spouse the year your spouse died.
2. Did not remarry before the last day of the tax year.
3. Have a child or stepchild (not a foster child) whom you can claim as a dependent, or could claim except that the child had gross income of $5,200 or more, filed a joint return, or you could be claimed as a dependent on someone else’s return.
4. Paid more than 50% of the cost of keeping a home that is the main home for you and your child for the entire tax year (except for temporary absences).

A qualifying surviving spouse uses the joint return tax rates and the married filing jointly standard deduction, while head of household rates are usually lower than the rates for single or married filing separately.

Filing deadlines

Individual tax returns (Form 1040) are due on the 15th day of the fourth month following the end of the tax year. For example, a 2025 tax return’s filing deadline is April 15, 2026. If the deadline falls on a Saturday, Sunday, or holiday, then the deadline will fall on the next business day. Taxpayers who need more time to gather information can use Form 4868 to file for an automatic 6-month extension until October 15th to file their tax return. Be aware that filing an extension does not give individuals more time to pay their balance due on their tax return. Interest and penalties will still accrue on the unpaid balance! Filing late costs 5% of the unpaid tax for each month or part of a month (the failure-to-file penalty, up to 25%), so a late return that shows a refund carries no penalty; paying late costs 0.5% per month (the failure-to-pay penalty, up to 25%), with or without an extension. U.S. citizens and resident aliens who live outside the U.S. and Puerto Rico and whose main place of business or post of duty is also outside the U.S. and Puerto Rico (or who are in military service on duty outside the U.S. and Puerto Rico) are granted an automatic 2-month extension, pushing the deadline to June 15th. Taxpayers who resided in a federally declared disaster area are granted extra time to file their tax return.

Signing under penalties of perjury. A Form 1040 isn’t a valid return unless it is signed, and both spouses sign a joint return. The signature sits under a declaration called the jurat: “Under penalties of perjury, I declare that I have examined this return and accompanying schedules and statements, and to the best of my knowledge and belief, they are true, correct, and complete.” A paid preparer also signs, and the preparer’s declaration “is based on all information of which preparer has any knowledge.” Using a preparer doesn’t shift responsibility: the taxpayer remains responsible for the correctness of the return. Willfully signing a return under penalties of perjury that the signer doesn’t believe is true and correct as to every material matter is a felony under IRC §7206(1), punishable by a fine of up to $100,000, up to 3 years in prison, or both.