Understanding US sales tax compliance: What small businesses need to know

Tax compliance can often feel like navigating a spider’s web—complex, interconnected, and easy to get caught in. This challenge becomes even greater when it comes to US sales tax, where rates and rules vary across states, product categories, nexus requirements, and sales thresholds. For businesses operating across multiple jurisdictions, staying compliant can quickly become a daunting task.

Whether you're selling products online, operating a retail store, or providing taxable services, understanding your sales tax obligations is critical to avoiding penalties and maintaining compliance.

What is sales tax?

Sales tax is a consumption tax that businesses in the United States are required to collect from customers and remit to the appropriate state or local tax authority. Unlike many countries that impose a national value-added tax (VAT) or federal sales tax, in the US, sales tax is generally administered at the state and local levels, with each jurisdiction establishing its own rules and rates.

Although the tax is ultimately borne by the customer, businesses play a critical role in the process. They are responsible for calculating the applicable sales tax on taxable transactions, collecting it at the point of sale, maintaining accurate records, and remitting the collected amount to the relevant tax authority.

Adding to the complexity, sales tax regulations vary significantly from state to state. Each state determines who is required to collect sales tax, which products and services are taxable, applicable tax rates, registration requirements, filing frequencies, and exemption rules. As a result, businesses that operate in multiple states must understand and comply with the sales tax requirements of each jurisdiction where they have a tax obligation.

When does a business have a sales tax obligation?

Not every business is required to collect and remit sales tax in every state. A sales tax obligation arises when a business establishes a sufficient connection, known as sales tax nexus, with a state or local jurisdiction.

Sales tax nexus refers to the relationship between a business and a taxing authority that creates the responsibility to register, collect, and remit sales tax. Broadly, there are two primary types of nexus that can trigger this obligation.

Physical nexus is the traditional standard for establishing a sales tax obligation. A business may create physical nexus in a state by maintaining a physical presence there, such as an office or retail location, a warehouse or distribution center, inventory stored within the state, or employees, contractors, or sales representatives operating in the state.

Economic nexus is based on a business's economic activity within a state rather than its physical presence. A business may establish economic nexus when its sales revenue or transaction volume exceeds a state's specified threshold.

These thresholds vary by state, but they are commonly based on:

• Total sales revenue generated within the state

• Number of transactions completed in the state

• A combination of both factors

The concept of economic nexus gained prominence following the 2018 Supreme Court ruling in South Dakota v. Wayfair, Inc. The decision allowed states to require out-of-state sellers to collect and remit sales tax based on their economic activity within the state, even if they do not maintain a physical presence there.

Since the ruling, most states have adopted economic nexus laws, although the specific thresholds and compliance requirements differ by jurisdiction. As a result, businesses selling across state lines should regularly monitor their sales activity to determine where they may have established a sales tax obligation.

Determining whether your products or services are taxable

Establishing a sales tax nexus is only one part of compliance. Businesses must also determine whether the products or services they sell are subject to sales tax in the states where they operate.

Not all products and services are taxable. While many goods and services are subject to sales tax, certain categories may be exempt or taxed at a reduced rate depending on the state's laws.

In most states, tangible personal property—physical items that can be seen, touched, and purchased—is generally taxable. This includes clothing and apparel, electronics, furniture, household goods, and similar items.

However, some states provide exemptions or reduced tax rates for specific categories of products, such as groceries, prescription medications, medical devices, or manufacturing equipment.

The taxability of services is even more complex and varies significantly by state. While some states tax only a limited range of services, others impose sales tax on most offerings. Examples of services that may be taxable in certain states include: software and digital services, telecommunications services, repair and maintenance services, information and data-processing services, and personal care services.

Given the variations in state tax laws, businesses should regularly review the taxability of their products and services to ensure they are collecting the correct amount of sales tax and maintaining compliance with applicable regulations.

Registering for a sales tax permit

Once a business establishes a sales tax nexus in a state, it must register for a sales tax permit before collecting sales tax from customers. Collecting sales tax without the appropriate permit can result in penalties and compliance issues.

The registration process generally involves the following steps:

• Determine where your business has established nexus.

• Apply for a sales tax permit with the relevant state tax authority.

• Obtain the permit or registration certificate.

• Configure your billing, accounting, or ecommerce systems to collect the correct sales tax rates.

After registration, businesses can begin collecting, reporting, and remitting sales tax in accordance with the state's requirements.

Collecting the correct amount of sales tax

Calculating sales tax in the US can be challenging because tax rates are not determined solely at the state level. In many jurisdictions, counties, cities, and special taxing districts can impose additional sales taxes, resulting in a combined tax rate that varies based on the location of the sale.

Another important consideration is sales tax sourcing, which determines the tax rate that should be applied to a transaction. There are two primary sourcing methods:

1. Origin-based sourcing – Sales tax is calculated based on the seller's business location.

2. Destination-based sourcing – Sales tax is calculated based on the location where the buyer receives the product or service.

For businesses that sell and ship products across states, destination-based sourcing is the prevailing rule in most states. Given the varying tax rates and sourcing rules, businesses should ensure they apply the correct tax rate to every transaction to avoid compliance issues and potential penalties

Filing and remitting sales tax

After collecting sales tax from customers, businesses are required to file sales tax returns and remit the collected tax to the appropriate state tax authority.

Depending on the state's requirements, sales tax returns may need to be filed on a monthly, quarterly, or annual basis. When filing a return, businesses must report their taxable sales, calculate the tax due, and remit the collected amount.

To avoid penalties and interest charges, businesses should ensure returns are filed accurately and payments are made on time according to the state's filing schedule.

Common sales tax mistakes small businesses make 

Sales tax compliance can be complex, even small mistakes can result in penalties and audits. Some of the most common errors businesses make include:

• Failing to register for a sales tax permit after establishing nexus

• Collecting incorrect sales tax rates

• Missing filing and payment deadlines

• Not obtaining or retaining valid exemption certificates

• Assuming all services are exempt from sales tax

• Overlooking marketplace facilitator and reporting requirements

Regularly reviewing your sales tax obligations and maintaining accurate records can help avoid these common compliance pitfalls.

How the right accounting software can help

Managing sales tax manually can be overwhelming, especially for businesses operating across multiple states with varying tax rates, taxability rules, and filing requirements. Tracking changing regulations while ensuring accurate tax collection can consume valuable time and increase the risk of costly errors.

This is where technology can make a significant difference. Modern accounting software can automate many aspects of sales tax compliance, including tax calculations, tax categorization, record keeping, and reporting, helping businesses reduce manual effort and improve accuracy.

Zoho Books simplifies sales tax management by automatically calculating applicable sales taxes and determining the correct tax treatment based on factors such as what you're selling, who you're selling to, and where the transaction takes place. It also supports exemption certificate management and provides detailed sales tax liability reports, giving businesses greater visibility into their tax obligations.

By automating routine tax processes, businesses can spend less time worrying about compliance and more time focusing on growth.

Sign up for free and make taxation feel less taxing.