U.S. individual tax guide for founders, expats, investors, and complex households | Antravia Advisory

The United States individual tax system is built on a set of rules that interact with each other in ways that are not always obvious from the outside. Your filing status affects your brackets. Your adjusted gross income affects your eligibility for deductions and credits. Your investment decisions affect your capital gains treatment. Your retirement withdrawals can push other income into a higher bracket. And if you have cross-border income, foreign assets, or business interests layered on top of all of that, the interactions multiply.

This guide is designed for people whose tax situation has moved beyond the standard. Founders with business income and equity. Expats managing income across two countries. Investors with capital gains, rental property, and retirement accounts. Households where the return requires judgment, not just data entry.

Each section below covers one area of individual US tax. The key figures shown are current for 2025 and 2026 so you can plan with the right numbers. Every section links to a full article where the topic is examined in depth.

Part 1 Filing Basics: Who Files, When, and How

Before any income is calculated or any deduction is claimed, a US tax return is built on a foundation of decisions that most people make without thinking about them carefully. Your filing status determines your tax brackets, your standard deduction, and your eligibility for a range of credits. Whether you can claim someone as a dependent affects your household's overall tax position. Your taxpayer identification number is the key that makes all of it work.

This section explains who is required to file a US federal return, the five filing statuses and when each one applies, how dependents are determined and why it matters, the filing deadlines and extension mechanics, and the difference between the extension of time to file and the obligation to pay. It also explains why estimated tax payments exist and when they apply, and why treating tax as a once-a-year event rather than an ongoing obligation creates unnecessary exposure.

Key figures

Filing deadline: 2025: April 15, 2026 | 2026: April 15, 2027

Extension deadline: 2025: October 15, 2026 | 2026: October 15, 2027

Estimated tax payment penalty threshold: 2025: 90% of current year or 100% of prior year tax | 2026: same

Part 2 Wages, Interest, Dividends, and Ordinary Income

The most common income types on a US return are wages, salary, interest, and dividends. Most people understand roughly what these mean, but the tax treatment of each has layers that matter when income reaches meaningful levels.

Qualified dividends are taxed at preferential long-term capital gains rates rather than ordinary income rates. Interest from municipal bonds is generally exempt from federal income tax. Certain employer benefits are excluded from taxable wages entirely. The distinction between ordinary dividends and qualified dividends can be worth thousands of dollars annually for investors with significant equity portfolios. This section maps the most common income categories, explains what is taxable and what is not, and identifies the points where the standard assumptions break down.

Key figures

Top ordinary income rate: 2025: 37% above $626,350 single / $751,600 MFJ | 2026: 37% above $640,600 single / $768,700 MFJ

Qualified dividend rate (top bracket): 2025: 20% | 2026: 20%

Net Investment Income Tax (NIIT): 2025: 3.8% above $200,000 single / $250,000 MFJ | 2026: same thresholds

Part 3 Self-Employment and Freelance Income

Self-employment income in the United States carries a tax burden that surprises many people who are used to the employed model. You pay self-employment tax of 15.3% on net earnings up to the Social Security wage base, covering both the employer and employee share of Social Security and Medicare. That is on top of income tax at your marginal rate.

This section covers what constitutes self-employment income for US tax purposes, how Schedule C works, which business expenses are deductible and which are not, the home office deduction and its requirements, the mechanics of quarterly estimated tax payments, and why contractor status versus employee status creates very different tax outcomes. It also addresses the self-employment tax deduction, which allows you to deduct half of SE tax as an above-the-line adjustment, and the qualified business income deduction, which can reduce taxable income from pass-through businesses by up to 20%.

Key figures

Self-employment tax rate: 2025: 15.3% up to $176,100 SS wage base, 2.9% above | 2026: updated SS wage base applies

QBI deduction income threshold (phase-in): 2025: $197,300 / $394,600 MFJ | 2026: $201,775 for all other returns / $403,550 MFJ

SEP-IRA contribution limit: For self-employed individuals, the effective contribution rate is 20% of net earnings from self-employment (after deducting the contribution itself and half of self-employment tax).The 25% rate applies to employee compensation in non-self-employed contexts, but self-employed calculations adjust it downward to an effective ~20%. 2025: up to $70,000 | 2026: up to $72,000

Part 4 Investment Income, Capital Gains, and Property Transactions

Capital gains tax treatment is one of the most misunderstood and most consequential areas of individual US tax. The difference between a short-term gain taxed at your ordinary income rate and a long-term gain taxed at 0%, 15%, or 20% depends on a single factor: whether you held the asset for more than one year. For investors making timing decisions around equity sales, property disposals, or fund switches, this distinction can be worth tens of thousands of dollars.

This section covers cost basis and why getting it right matters, short-term versus long-term capital gains treatment, the taxation of stock sales and fund redemptions, capital loss limitations and the $3,000 annual deduction cap against ordinary income, the primary residence exclusion of up to $500,000 for married couples, the basic US tax framework for rental property including depreciation, and the specific complexity that arises when property or investments are held across borders.

Key figures

0% LTCG rate threshold: 2025: Up to $48,350 single / $96,700 MFJ | 2026: Up to $49,550 single / $99,100 MFJ

15% LTCG rate threshold: 2025: $48,350 to $533,400 single / $96,700 to $600,050 MFJ | 2026: adjusted for inflation

Primary residence exclusion: 2025: $250,000 single / $500,000 MFJ | 2026: same

Annual capital loss deduction cap: 2025: $3,000 against ordinary income | 2026: $3,000 against ordinary income

Part 5 Retirement Income and Social Security

Retirement accounts in the United States operate on a deferred tax model. Traditional IRA and 401(k) contributions reduce taxable income now, with tax paid when withdrawals are made. Roth accounts work in reverse: contributions are made from after-tax income, but qualified withdrawals are tax-free. The choice between these two models, and the timing of withdrawals, has a significant effect on lifetime tax outcomes.

This section covers the tax treatment of traditional and Roth account distributions, pension and annuity income, early withdrawal penalties and the exceptions that apply, rollover mechanics and the rules that govern them, required minimum distributions from age 73, and when Social Security benefits become partially taxable. It also addresses the planning implications of retirement income for UK expats, where a UK pension sits alongside a US retirement account and both must be managed within the same overall tax picture.

Key figures

401(k) employee contribution limit: 2025: $23,500 | 2026: $24,500

401(k) catch-up limit (age 50+): 2025: $7,500 | 2026: $8,000

IRA contribution limit: 2025: $7,000 | 2026: $7,500

IRA catch-up limit (age 50+): 2025: $1,000 | 2026: $1,100

Early withdrawal penalty: 2025: 10% plus ordinary income tax | 2026: same

RMD start age: 2025: 73 | 2026: 73

Part 6 Adjustments to Income

Adjustments to income, sometimes called above-the-line deductions, are deductions that reduce your adjusted gross income before you reach the point of choosing between the standard deduction and itemizing. This matters because AGI is the figure that determines eligibility for many other tax benefits. A lower AGI can unlock deductions and credits that would otherwise be reduced or eliminated by phaseout rules.

This section explains what adjustments to income are and why they are more valuable than below-the-line deductions for many taxpayers, covers the most common adjustments including the self-employed health insurance deduction, deductible IRA contributions, student loan interest, HSA contributions, and one-half of self-employment tax, and explains how these interact with phaseout thresholds for other benefits. For founders and self-employed individuals, this section identifies the adjustments that are most commonly missed.

Key figures

HSA contribution limit (self-only): 2025: $4,300 | 2026: $4,400

HSA contribution limit (family): 2025: $8,550 | 2026: $8,750

Traditional IRA deduction phaseout (single, workplace plan): 2025: $79,000 to $89,000 | 2026: adjusted for inflation

Traditional IRA deduction phaseout (MFJ, workplace plan): 2025: $126,000 to $146,000 | 2026: adjusted for inflation

Part 7 Standard Deduction and Itemized Deductions

Every US taxpayer faces a binary choice: take the standard deduction or itemize. You cannot do both. For most taxpayers, the standard deduction is now the correct choice following the significant increases introduced under the Tax Cuts and Jobs Act and made permanent in 2025. But for homeowners with large mortgages, significant charitable givers, or those with high state and local taxes, itemizing may still produce a better outcome.

This section covers the current standard deduction amounts, the additional deduction available for taxpayers aged 65 and over, and the new senior bonus deduction introduced in 2025. It explains the key itemized deductions including mortgage interest, state and local taxes, charitable contributions, and medical expenses, the SALT deduction cap and the temporary increases under the One Big Beautiful Bill Act, and the circumstances in which itemizing makes financial sense. It also addresses the specific position of non-US persons and dual-status filers, for whom the standard deduction rules differ.

Key figures

Standard deduction (single): 2025: $15,750 | 2026: $16,100

Standard deduction (MFJ): 2025: $31,500 | 2026: $32,200

Standard deduction (HoH): 2025: $23,625 | 2026: $24,150

Additional deduction (age 65+, single): 2025: $2,000 | 2026: $2,050

Additional deduction (age 65+, MFJ): 2025: $1,600 per qualifying spouse | 2026: $1,650 per qualifying spouse

Senior bonus deduction (new from 2025): 2025: Up to $6,000 per filer, phases out above $75,000 single / $150,000 MFJ | 2026: same

SALT deduction cap: For 2025, the IRS says the SALT cap was increased to $40,000 ($20,000 MFS), with a reduction above $500,000 MAGI ($250,000 MFS), but not below $10,000 ($5,000 MFS).

Part 8 Tax Credits

Tax credits are more valuable than deductions because they reduce your tax liability dollar for dollar rather than reducing the income on which tax is calculated. A $1,000 deduction saves you $220 if you are in the 22% bracket. A $1,000 credit saves you $1,000. The distinction matters enormously for planning purposes, yet credits are frequently claimed incorrectly, claimed when ineligible, or missed entirely.

This section explains the difference between refundable and nonrefundable credits and why it matters, covers the child tax credit and the additional child tax credit, the earned income credit and its income limitations, education credits including the American Opportunity Tax Credit and the Lifetime Learning Credit, the child and dependent care credit, and the retirement savings contribution credit. It also explains why credit eligibility is often narrower than it appears and how phaseout rules reduce or eliminate credits as income rises.

Key figures

Child tax credit (per qualifying child): 2025: $2,200 (refundable portion $1,700) | 2026: $2,200

EITC maximum (3+ children): 2025: $8,046 | 2026: $8,231

American Opportunity Tax Credit maximum: 2025: $2,500 per eligible student | 2026: $2,500

Child and dependent care credit: 2025: Up to $3,000 for one child / $6,000 for two or more | 2026: same

Part 9 Tax Payments, Penalties, Refunds, and Amended Returns

Filing a correct return is only part of the obligation. Tax must also be paid correctly and on time. The US system operates on a pay-as-you-go basis, meaning tax is expected to be paid throughout the year through withholding or estimated payments, not just at the filing deadline. Underpayment during the year triggers a penalty even if the full amount is paid by April 15.

This section explains how withholding from wages works and how to adjust it, how estimated quarterly tax payments work and when they are required, the safe harbor rules that protect against underpayment penalties, the distinction between the failure-to-file penalty of 5% per month and the failure-to-pay penalty of 0.5% per month, how refunds work and why a large refund is not the same as good tax planning, and how to correct errors through an amended return on Form 1040-X. It also addresses what happens when a return is extended and payment is not made, which is one of the most common and most preventable tax mistakes.

Key figures

Failure-to-file penalty: 2025: 5% per month up to 25% of tax due | 2026: same

Failure-to-pay penalty: 2025: 0.5% per month up to 25% of tax due | 2026: same

Estimated tax due dates: 2025: April 15, June 16, September 15, January 15 | 2026: same cycle

Amended return deadline: 2025: 3 years from original filing deadline or 2 years from payment, whichever is later | 2026: same

Part 10 Cross-Border and Complex Individual Issues

For a growing proportion of individuals filing US returns, the standard domestic tax framework is only part of the picture. Founders with foreign corporate interests, expats managing income across two tax systems, investors with foreign financial accounts, and households with cross-border family arrangements all face layers of complexity that standard US tax preparation does not address.

This section covers the resident versus non-resident distinction and how it determines which income is taxable in the US, the foreign tax credit and how it prevents double taxation on income taxed abroad, the Foreign Earned Income Exclusion and who qualifies, foreign account reporting requirements including the FBAR and Form 8938, the treaty framework that governs income flows between the US and its treaty partners including the UK, and the specific situations that require moving beyond standard individual tax advice to cross-border specialisation. It explains when a general tax preparer is adequate and when the complexity of the situation requires a different level of expertise.

Key figures

Foreign Earned Income Exclusion: 2025: $130,000 | 2026: $132,900

FBAR filing threshold: 2025: $10,000 aggregate at any point during the year | 2026: same

Form 8938 threshold (single, US resident): 2025: $50,000 year-end or $75,000 at any point | 2026: same

Form 8938 threshold (MFJ, US resident): 2025: $100,000 year-end or $150,000 at any point | 2026: same

About this guide

This guide is published by Antravia Advisory. Each section above links to a full article covering the topic in depth with current figures, worked examples, and the specific nuances that matter for founders, expats, investors, and complex households. The guide is updated for 2025 and 2026 figures reflecting the One Big Beautiful Bill Act signed into law in July 2025.

Antravia Advisory is a cross-border tax and advisory firm. We work with clients whose tax situations require more than standard preparation.

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