From Start to Finish | The Essential U.S. Tax Compliance Guide for Antom Merchants

When your independent e-commerce store, AI/SaaS product, game, or short-form content business begins to gain momentum in the U.S. market and orders start pouring in, an unfamiliar challenge often emerges: U.S. tax compliance.

Do any of these questions sound familiar?

• “How large must my business be before I’m required to register a company in the United States?”

• “I’m receiving orders from dozens of U.S. states. Does that mean I must pay tax in each one?”

• “I only sell digital goods or SaaS services. Do I still need to charge sales tax?”

• “I’ve heard U.S. tax penalties can be harsh. How do I avoid compliance risks?”

You’re certainly not the only one asking.

At Antom, we recognise that many overseas SMEs don’t have the support of a dedicated compliance team. This guide breaks down, step by step, the essential principles of U.S. tax compliance, helping you navigate requirements with confidence and clarity.

Part I: The Foundation: Understanding Your U.S. Tax Obligations

What taxes do I need to pay when selling in the U.S.?

Operating in the United States generally involves two major types of tax:

• Sales Tax
• Income Tax

Understanding the distinction between them is the first step towards compliance.

1. Sales Tax: A Tax on Transactions

• Nature: Paid by the consumer; collected and remitted by the merchant
• Levied by: State and local governments
• Tax rate:
  Total rate = State rate + County/City rate 
  Typical range: 6%–10% 

• Scope: Not limited to physical goods, digital products (SaaS, games, streaming or short-form content) are taxable in most states

Sales Tax Calculation Example

Physical Product Example

You sell a product for $100 to a customer located in Los Angeles, California.

• California state tax: 7.25%
• Los Angeles local tax: 2.25%
• Total sales tax rate: 9.5%
  

Calculation:

• Sales tax = $100×9.5% = $9.50
• Total amount paid by customer = $109.50

2. Income Tax: A Tax on Profits

• Nature: Taxed on your profits; borne by the company
• Levied by: Federal government + State governments
• Tax rates:
  Federal corporate income tax: 21% (flat rate)
  State corporate income tax: 0%-12%, depending on the state (e.g. California ≈ 8.84%)
• Filing requirement: Even if you are not required to collect sales tax, profitable activity may still trigger income tax obligations⸻

What Is Nexus? Why Does It Matter?

Nexus is the determining threshold that decides whether you are required to pay tax in a particular state. Once Nexus is triggered, you must register, collect, and file taxes in that state.

There are two main types of Nexus:

• Physical Nexus
• Economic Nexus

They apply differently to Sales Tax and Corporate Income Tax (CIT).

1. Sales Tax Nexus

• Physical Nexus

  • Triggered when you have warehouses, inventory, offices, and sales personnel within a state

  • Only employees directly related to sales activities count; pure customer support or back-office roles generally do not

• Economic Nexus 
  • Typical thresholds: $100,000 in annual sales or 200 transactions (most states)
  • Higher thresholds: California (CA) and New Jersey (NJ): $500,000 in annual sales
  • Once exceeded: Register for a sales tax permit; begin collecting and filing sales tax

2. Income Tax Nexus (Corporate Income Tax)

• Physical Nexus

  • Triggered if you have:

    • Fixed assets in the state

    • Any employees (sales, operations, or management)

• Economic Nexus

  • Triggered when state-sourced revenue exceeds statutory thresholds

  • Example:

    • California: $610,395

    • New York: $1,000,000

  • Not all profits are taxed in that state

  • Taxable income is allocated using state-mandated apportionment formulas (often a “three-factor formula”)

Key Differences

• Sales Tax Nexus: Focuses on selling to consumers in the state
• Income Tax Nexus: Focuses on earning income from the state

Once any Nexus condition is met, tax obligations arise, regardless of whether you have registered a U.S. company.

If You Do Not Have a U.S. Company

Even if you operate through a Chinese or other foreign entity:

• Nexus rules still apply to all entities, regardless of registration location
• You may need to apply directly to state tax authorities as a Foreign Entity
• This may involve: A Sales Tax Permit (Seller’s Permit); A State Income Tax ID

What to Do After Nexus Is Triggered

1. Sales Tax Nexus

• Register for a sales tax permit

• Begin collecting sales tax

• File and remit tax on time

2. Income Tax Nexus

• Register for a state income tax account
• If no U.S. entity exists:
  • Federal income tax filing is often required due to:
  • Federal–state tax dependency
  • IRS “Effectively Connected Income (ECI)” rules

Examples

• Company A:

  • Texas-registered LLC, no physical presence, annual sales in California exceed $500,000 → CA Sales Tax Economic Nexus 

• Company B:

  • New York C-Corp with employees in Illinois → IL Income Tax Physical Nexus

• Company C:

  • Chinese company with no U.S. entity, Washington State SaaS revenue exceeds $300,000 → WA Income Tax Economic Nexus

Antom Tips

• Sales tax and income tax Nexus rules are separate and must be assessed independently
• Hiring employees is a major tax risk trigger
• Build state-level sales monitoring systems early

Part II: Company Registration & Structure Before Entering the U.S. Market

Many merchants initially enter the U.S. market using overseas entities to keep operations lightweight. This is legally permitted, but it comes with limitations and risks.

Q1: Can I operate indefinitely without forming a U.S. company?

Yes. U.S. law does not require foreign companies to set up a U.S. entity to sell. However, once Nexus is triggered, you must register tax accounts and file returns as a Foreign Entity. Many merchants use this approach for early-stage market testing.

Q2: What are the drawbacks of not having a U.S. company?

• Certain licences, bank accounts, and payment channels require a U.S. entity
• Many B2B clients and platforms require a U.S. Tax ID or W-9
• Tax compliance is still possible, but brand credibility, fundraising and long-term local operations may be affected

Q3: When should I consider registering a U.S. company?

• Ongoing Nexus in one or more states
• Need for a U.S. bank account
• B2B partnerships with large U.S. enterprises
• Hiring local employees
• Licence or regulatory requirements

Antom Recommendation

Use an overseas entity during early testing. When sales approach state thresholds, plan ahead for U.S. entity registration or engage professional tax agents.

Choosing the Right U.S. Company Structure

Your company structure affects taxation, fundraising, shareholder eligibility, and compliance costs.

Note: Company structure does not affect Sales Tax Nexus obligations, which are determined by business activity location.

Entity Type Comparison: LLC vs. C Corp vs. S Corp

Antom Advice

Before final decisions, consult professional tax and legal advisers.

An LLC can later be converted to a C-Corp to support fundraising or listing plans.

Part III: Practical Compliance — Filing, Payment & Risk Prevention

Filing & Payment Methods

• Online filing: All states provide electronic systems (e.g. CA CDTFA, NY Tax Online)

• With a U.S. company: File using EIN and pay via ACH or credit card

• Without a U.S. company:

  • Register as a Foreign Entity and file using ITIN/EIN

  • Some states support international payments; due to complexity, local tax agents are recommended

Compliance Risks & Penalties

U.S. tax compliance is serious. The best defence is proactive compliance: timely registration, automation tools, complete records, and professional advice.

Common penalties

• Late filing penalties: Typically 5%–10% per month, some states double penalties after 2–3 months 

• Interest: Accrued daily, approx. 3%–6% annually 

• Civil penalties: Severe violations may incur 50%–100% of unpaid tax as fines 

• Criminal charges: Fraud, falsified records, or concealed income can affect credit, visas, and immigration status 

• Platform or bank freezes: Authorities may request platforms such as PayPal or Stripe to withhold funds 

Common compliance failures

• Failure to register after crossing thresholds
• Applying incorrect tax rates
• Late filings
• Under-reporting revenue across channels

Disclaimer

This guide is for general informational purposes only and does not constitute legal or tax advice.

U.S. tax laws are complex and subject to change. Always consult a qualified U.S. tax attorney or certified public accountant based on your specific circumstances.