Sales tax compliance is one of the most complex financial responsibilities for small and medium businesses. With changing state regulations, economic nexus laws, marketplace requirements, and multi-state filing rules, businesses must stay organized and compliant to avoid penalties, interest, and audit risks. This guide explains everything SMBs need to know about sales tax in a clear, practical format.
What Is Sales Tax?
Sales tax is a state-imposed tax on the sale of goods and certain services. Businesses are responsible for collecting, reporting, and remitting this tax to the correct state authority. Unlike income tax, sales tax rules vary widely from state to state.
Understanding Sales Tax Nexus
Nexus determines whether your business is legally required to collect sales tax in a state. There are two primary types:
1. Physical Nexus
You have physical nexus if your business has:
- A physical office or warehouse
- Employees or contractors working in the state
- Inventory stored in a fulfillment center (Amazon FBA counts)
- Regular in-state sales visits or trade show booths
2. Economic Nexus
Established after the South Dakota v. Wayfair ruling, states require remote sellers to collect sales tax once they pass certain thresholds.
Common thresholds include:
- $100,000 in annual sales, or
- 200 transactions shipped to that state
Each state sets its own rules, so multi-state businesses must monitor thresholds closely.
Products and Services That Are Taxable
Taxability varies by state, but common taxable categories include:
- Tangible goods (electronics, medical supplies, tools, etc.)
- Digital products (software, eBooks, subscriptions)
- Certain services such as repair, installation, and SaaS
Exempt items may include groceries, medications, and resale purchases. Always maintain exemption certificates for compliance.
Collecting Sales Tax Correctly
To collect sales tax, businesses must:
- Register for a state sales tax permit
- Charge tax at the correct rate (state, county, and local)
- Use destination-based sourcing for most states
- Verify taxability of products and exemptions
- Record tax collected and reconcile monthly
Filing Sales Tax Returns
Most states assign filing frequencies based on total sales tax collected:
- Monthly for higher-volume sellers
- Quarterly for mid-volume sellers
- Annual for low-volume sellers
Businesses must file even if no sales tax was collected during the period. This is known as a zero return.
Sales Tax Penalties and Interest
States impose strict penalties for late or inaccurate filings:
- Late filing penalties (5% to 25%)
- Late payment penalties
- Daily interest accrual
- Loss of vendor discounts
- Audit triggers
Multi-State Sales Tax Compliance
If you sell across multiple states (e-commerce, wholesale, Amazon FBA), you must:
- Track nexus in every state
- Register in states where nexus exists
- Set correct tax rates per location
- File separate sales tax returns for each state
- Maintain exemption certificates for B2B clients
Sales Tax Automation Tools
Automation reduces compliance risk. Common tools include:
- Avalara AvaTax
- TaxJar
- QuickBooks Sales Tax Center
- Shopify Tax
These tools automatically calculate rates, monitor nexus thresholds, and prepare filings.
Sales Tax Audit Preparation
States conduct audits to verify if sales tax was collected and remitted accurately. Keep the following ready:
- Sales reports by state
- Exemption certificates
- Purchase invoices
- Tax calculation logic
- Filing confirmations
- Bank statements
Proper recordkeeping reduces audit risk and speeds up the process.
State-Specific Example: Florida Sales Tax
Florida requires businesses to:
- Register with the Florida Department of Revenue
- Collect sales tax on taxable goods and some services
- File monthly or quarterly returns via the online portal
- Maintain resale certificates for B2B transactions
Local surtax also applies based on county.
Best Practices for Sales Tax Compliance
- Reconcile sales tax collected monthly
- Keep product taxability charts updated
- Review nexus exposure quarterly
- Use automation to calculate rates
- Maintain digital records for at least seven years