Tax basics for beginners (United States)

Marginal tax brackets

For ordinary taxable income, U.S. federal income tax is progressive: slices of taxable income are taxed at different rates. Entering a higher bracket applies that higher rate only to the slice in that bracket, not to all your income. Bracket thresholds depend on your tax year and filing status. Some income, including certain long-term capital gains and qualified dividends, follows different rate rules.

Deductions vs. credits

A deduction reduces taxable income; a credit reduces the tax owed, dollar for dollar. Eligible filers generally compare the standard deduction with allowable itemized deductions, but eligibility rules and exceptions apply. Some deductions can be available without itemizing. A $100 deduction does not normally save $100 of tax.

Nonrefundable credits generally reduce eligible tax only to zero. Refundable credits can produce a refund beyond the tax owed; some credits are only partly refundable. Eligibility, income limits and other restrictions depend on the credit and tax year.

Withholding and refunds

Employers generally withhold federal income tax from paychecks using your pay and Form W-4 information. When your return is calculated, withholding, estimated payments and applicable credits are compared with your tax liability. A refund can come from overpayments or refundable credits, not just excess withholding. A balance due means those payments and credits did not cover the amount owed.

Check withholding each January and after major changes such as marriage, a new job or a significant income change. If an adjustment is needed, submit an updated Form W-4 to your employer. The IRS Tax Withholding Estimator explains who can use it and what records are needed.

Side income

Gig and freelance income is generally taxable and must be reported when you are required to file, even if no information form arrives or you are paid in cash. Keep income and expense records; not every expense is deductible. Self-employed people may owe self-employment tax as well as income tax.

Tax is generally paid as income is earned through withholding or estimated payments. Depending on your expected tax, withholding, credits and other rules, estimated payments may be required. The IRS uses four payment periods with specific due dates, not four equal calendar quarters. Some wage earners can cover additional income by increasing withholding. Check the IRS estimated-tax guidance for requirements, exceptions, due dates and possible underpayment penalties.

Filing status and taxable income are different steps

Filing status affects tax brackets, the standard deduction, filing requirements and eligibility for certain benefits. The five federal statuses are single, married filing jointly, married filing separately, head of household and qualifying surviving spouse. Each has eligibility rules; head of household is not simply another name for being single or paying rent. Use the IRS filing-status guidance for your circumstances.

Gross income, adjusted gross income (AGI) and taxable income are not interchangeable. AGI generally starts with income and subtracts qualifying adjustments. Taxable income then reflects applicable deductions. Some eligibility rules use modified adjusted gross income (MAGI), whose definition can differ by provision. Do not substitute take-home pay or the total of bank deposits for these tax figures.

Keep the records behind the numbers

Gather relevant wage statements, income forms, payment records and documents supporting deductions or credits. A transaction category alone does not prove that an expense is deductible. For business costs, keep records of the amount and business purpose, and separate personal from business spending. An income form is a reporting aid, not the definition of everything you earned.

How long to keep a record depends on what it supports and the applicable limitations period; there is no single retention period for every situation. Property records, unfiled returns and other circumstances can require different treatment. Check the IRS recordkeeping guidance before discarding documents, and protect them from unauthorized access.