Tax Form Knowledge Base

Form 1040

U.S. Individual Income Tax Return

Plain English: The standard annual return you send to the IRS to calculate how much income tax you owe (or how much refund you get back).

Who Needs It: Most US Residents
Typical Deadline: April 15

Form 1040-NR

Nonresident Alien Income Tax Return

Plain English: For people who work or earn money in the U.S. but aren't considered residents for tax purposes (like some expats or visa holders).

Who Needs It: Non-Resident Aliens
Typical Deadline: April 15 / June 15

Form 1120-S

U.S. Income Tax Return for an S-Corp

Plain English: Used by S-Corporations to report their profits, which "pass through" to the owners' personal tax returns.

Who Needs It: S-Corp Shareholders
Typical Deadline: March 15

Form 1065

U.S. Return of Partnership Income

Plain English: An information return for businesses owned by two or more people to show how money was split among partners.

Who Needs It: Partnerships & LLCs
Typical Deadline: March 15

Form W-7

Application for IRS Individual TIN

Plain English: Used to request a tax ID number (ITIN) if you aren't eligible for a Social Security Number but still need to file taxes.

Who Needs It: ITIN Applicants
Typical Deadline: When Filing Return

FinCEN 114 (FBAR)

Report of Foreign Bank Accounts

Plain English: A report telling the Treasury about your bank accounts outside the U.S. if the total across all accounts exceeds $10k.

Who Needs It: Account Holders > $10k
Typical Deadline: April 15 (Auto-Ext)

Form 5471

Info Return of U.S. Persons w.r.t. Foreign Corporations

Plain English: Filed by US persons who own or control a foreign corporation. Missing it triggers a $10,000+ penalty per year.

Who Needs It: US Owners of Foreign Corps
Typical Deadline: With 1040 (Apr 15)

Form 5472

Info Return — Foreign-Owned U.S. Corporation

Plain English: Required for foreign-owned U.S. LLCs and corporations. Missing it starts at $25,000 per form, per year.

Who Needs It: Foreign-Owned U.S. Entities
Typical Deadline: April 15

Form 8938

Statement of Specified Foreign Financial Assets

Plain English: FATCA disclosure of foreign financial assets when totals exceed the reporting threshold ($50k–$600k depending on status).

Who Needs It: US Persons w/ Foreign Assets
Typical Deadline: With 1040 (Apr 15)

Form 8833

Treaty-Based Return Position Disclosure

Plain English: Attached to your return when you're claiming an income tax treaty benefit above the disclosure threshold.

Who Needs It: Treaty Claimants
Typical Deadline: With Return

Form 1120

U.S. Corporation Income Tax Return

Plain English: The standard C-Corporation tax return, reporting corporate income, deductions, and tax owed.

Who Needs It: C-Corporations
Typical Deadline: April 15

Schedule C

Profit or Loss from Business (Sole Prop)

Plain English: Attached to Form 1040 to report self-employment or single-member LLC income and expenses.

Who Needs It: Sole Proprietors
Typical Deadline: April 15

Schedule E

Supplemental Income (Rental / Royalty)

Plain English: Reports rental real estate income, royalties, and pass-through income from partnerships or S-corps.

Who Needs It: Landlords & K-1 Recipients
Typical Deadline: April 15

Form 4868

Application for Automatic Extension

Plain English: Grants an automatic 6-month extension to file your 1040. Does not extend time to pay — interest still accrues.

Who Needs It: Anyone Needing More Time
Typical Deadline: April 15

CP2000

Automated Underreporter Notice

Plain English: IRS notice sent when income reported on your return doesn't match what payers reported. Not a bill — response is required.

Who Needs It: Notice Recipients
Typical Deadline: 30 days from notice

CP504

Intent to Levy Notice

Plain English: An urgent IRS notice indicating intent to seize state refunds and eventually other assets to satisfy unpaid tax debt.

Who Needs It: Delinquent Taxpayers
Typical Deadline: Respond immediately

Essential IRS Forms