How to File Sales Tax Returns
Understanding Filing Frequencies
Each state assigns you a filing frequency when you register for your sales tax permit, based on the amount of tax you are expected to collect. Monthly filing is assigned to sellers collecting roughly $300 or more per month in tax, which corresponds to approximately $4,000+ per month in taxable sales at an average 8% rate. Quarterly filing is for moderate-volume sellers, typically collecting $100 to $300 per month. Annual filing is for low-volume sellers collecting less than $100 per month. These thresholds vary by state, and states can change your filing frequency as your sales volume changes.
Filing frequency directly affects your cash flow and administrative burden. Monthly filing means 12 returns per year per state, but it keeps the amount of tax you are holding (and must eventually remit) smaller. Quarterly filing means 4 returns per year, which is more manageable but means you are sitting on three months of collected tax at a time. If you are registered in 15 states and filing quarterly in all of them, you are filing 60 returns per year, or about 5 per month. This is where the administrative burden of multi-state compliance becomes a significant time investment, and where auto-filing services provide the most value.
Step-by-Step Filing Process
Pull transaction reports from every selling channel where you made sales during the period: your direct ecommerce store (Shopify, WooCommerce, BigCommerce), any marketplaces (Amazon, Etsy, eBay, Walmart), and any offline or invoiced sales. For each transaction, you need the customer's shipping address (state, county, city, and ZIP code), the total sale amount, any exempt amounts, and the tax collected. If you use sales tax software like TaxJar or Avalara, this data is aggregated automatically from all connected channels.
Most states require you to report sales tax broken down by local jurisdiction, not just at the state level. A state like New York has over 900 local tax jurisdictions. California has hundreds of special tax districts. You need to allocate each transaction to the correct county, city, and special district based on the customer's shipping address. This is the step that makes manual filing extremely time-consuming for multi-jurisdiction states, because you must determine the correct local allocation for every transaction. Tax automation software handles this allocation automatically using address-level geo-coding.
For each jurisdiction on the return, calculate your gross sales (total revenue from all transactions), exempt sales (non-taxable sales, resale certificate sales, and sales of exempt products), taxable sales (gross sales minus exempt sales), tax rate for that jurisdiction, expected tax at that rate, and actual tax collected. If the actual tax collected differs from the expected amount (due to rounding or rate discrepancies), you report the tax collected and the state reconciles any small differences. Large discrepancies indicate a configuration problem in your tax calculation that needs to be investigated.
Log into the state's electronic filing portal using your sales tax account credentials. Enter the data from your calculations into the return form. Most state portals walk you through each section: gross sales, deductions (exempt sales, returns, marketplace sales where the marketplace remitted tax), net taxable sales, and tax due. Review the return for accuracy before submitting. Some states like New York and California have complex multi-page returns with dozens of line items, while others like South Dakota have streamlined single-page forms.
Approximately 25 states offer a timely filing discount (also called a vendor discount or collection allowance) that lets you keep a small percentage of the tax you collected as compensation for acting as the state's tax collector. Discounts typically range from 0.5% to 5% with a dollar cap per period. For example, Ohio allows 0.75% of the tax collected. Florida allows 2.5% up to $30 per reporting period. Texas allows 0.5% up to $10,000 per period. The discount is only available if you file and pay on time, so a late filing forfeits the discount even if you pay the full amount of tax.
Most states require payment via ACH debit or electronic funds transfer (EFT) for remote sellers. Some states accept credit card payments, though processing fees apply (typically 2% to 3%). Submit payment at the same time as your return or by the payment deadline if it differs from the filing deadline. Save your confirmation number, a screenshot or PDF of the filed return, and proof of payment. Maintain these records for at least 4 years, or longer if the state has an extended statute of limitations.
Handling Marketplace Sales on Returns
If you sell on Amazon, Etsy, eBay, or other marketplaces, those platforms collect and remit sales tax on your behalf under marketplace facilitator laws. However, most states still require you to report those marketplace sales on your return, even though you are not remitting tax on them. The return typically has a line for "marketplace sales" or "sales where tax was collected by a marketplace facilitator," which you report as a deduction from your gross sales.
This creates a confusing situation where your return shows high gross sales but low taxable sales because the marketplace already handled the tax on most of your transactions. The net tax due on your return is only for your direct sales (Shopify store, WooCommerce store, invoiced sales). It is critical to separate marketplace transactions from direct transactions in your data to avoid accidentally remitting tax on marketplace sales that the marketplace already paid, which would result in double taxation.
Zero-Dollar Returns
If you made no sales in a state during a filing period, you still must file a return showing zero gross sales and zero tax due. This is commonly called a "zero return" or "zero-dollar return." Failing to file zero returns triggers late filing penalties in every state, and accumulated unfiled returns can lead to permit revocation, estimated assessments (where the state guesses what you owe based on previous periods or industry averages), and collections actions.
If you no longer sell into a state and do not anticipate future sales there, the correct action is to close your sales tax account in that state rather than continue filing zero returns indefinitely. File any outstanding returns, pay any remaining tax, and then contact the state's department of revenue to request account closure. Until the account is officially closed, the filing obligation continues.
Late Filing: Penalties and Interest
Every state imposes penalties for late filing and late payment. The typical penalty structure includes a late filing penalty (5% to 25% of the tax due per month or fraction of a month, up to a cap), a late payment penalty (similar percentage structure), and interest on the unpaid tax from the due date until the date of payment. In some states, the combined late filing and late payment penalties can reach 25% to 50% of the tax due within just a few months of the deadline.
The penalty applies even for small amounts. If you owe $50 in tax and file one month late, the penalty might be $5 to $12.50 plus interest. If you consistently file late across 10 states, these small penalties compound into significant costs. Setting up automated filing through TaxJar or Avalara eliminates the risk of missed deadlines entirely, which for many sellers is worth the filing fee alone.
Using AutoFile Services
AutoFile is TaxJar's automated filing service, and Avalara offers a comparable service called Avalara Returns. These services pull your transaction data from all connected channels, prepare the returns for each state, and file them electronically on your behalf by the deadline. The cost is typically $19.99 to $24.99 per state per month for TaxJar AutoFile, or included in Avalara's higher-tier plans. For a seller filing in 10 states monthly, the cost is $200 to $250 per month for automated filing, which replaces 120 manual return filings per year.
The value of auto-filing increases with the number of states and the frequency of filing. A seller filing quarterly in 5 states (20 returns per year) might manage manually with a calendar and a spreadsheet. A seller filing monthly in 15 states (180 returns per year) is spending 20 to 30 hours per month on manual filing and is at constant risk of missed deadlines. At that scale, automated filing is not a luxury, it is a basic operational necessity. Our filing deadlines calendar shows exactly when each state's returns are due.