To file sales and use tax, log in to your state’s department of revenue portal, report your gross sales for the period, subtract documented exempt sales, apply the correct combined tax rate to what remains, add use tax on any business purchases where no sales tax was charged, and submit payment by the deadline your state assigned you. That is the whole cycle, repeated monthly, quarterly, or annually depending on your volume. The details below cover what to gather before you start, how to complete each line, how to claim the on-time filing discount that roughly 30 states offer, and what happens if you miss the deadline.
What to Have in Front of You Before You Start
Filing goes quickly when your records are ready and slowly when they aren’t. Pull together three things.
First, your total gross sales for the reporting period. That means everything you took in before deductions: cash, card, and barter. If you collect at different rates for different cities, counties, or special districts, break the total down by jurisdiction, because the return will ask you to.
Second, documentation for every sale you plan to claim as exempt. Resale certificates from wholesale buyers, exemption certificates from nonprofits and government agencies, and shipping records for out-of-state deliveries all belong here. A valid resale certificate should include the buyer’s name and address, their seller’s permit number, a description of what they’re buying, a statement that the goods are for resale, the date, and the buyer’s signature. If any of those elements are missing when an auditor looks, the state can hold you liable for the tax you didn’t collect. Some states treat certificates as valid indefinitely; others expire them in one to five years. Check yours and request updates before they lapse.
Third, a list of business purchases where the vendor didn’t charge sales tax. Office supplies bought from an out-of-state website that doesn’t collect your state’s tax, equipment picked up at a trade show in another state, inventory items you pulled for business use rather than resale. You owe use tax on these at the same rate a local purchase would carry, and the standard sales tax return in most states has a line for it. No separate form.
One boundary worth naming: if you sell through Amazon, Etsy, Walmart Marketplace, or a similar platform, the platform itself collects and remits sales tax on those transactions under state marketplace facilitator laws. You still report those sales on your return in most states, but the tax line for facilitated sales generally shows zero. If you sell both through a marketplace and through your own site, you are on the hook for the direct sales yourself. Keep those two channels clearly separated in your records.
Knowing Your Filing Frequency and Deadline
States assign filing frequency based on how much tax you collect. High-volume sellers file monthly, mid-range sellers quarterly, and small sellers annually. Frequency can be reassigned automatically as your collections cross thresholds, so a growing business may find itself bumped from quarterly to monthly without asking.
Monthly and quarterly returns are typically due by the 20th or the last day of the month following the reporting period. Annual returns are usually due in January for the prior calendar year. If the due date lands on a weekend or state holiday, it moves to the next business day.
Zero-sales periods still require a return in most states. Skipping a filing because you had no activity is one of the most common mistakes, and it draws the same late-filing penalty as a return with a balance due.
Completing the Return Line by Line
Nearly every state now files through an online portal. The labels and line numbers differ, but the structure is consistent.
Start with gross sales for the period. Enter the full amount before any deductions.
Next, subtract exempt sales. This typically includes resale transactions backed by certificates, sales to government entities, interstate shipments, and any product categories your state exempts. Groceries, clothing, and prescription drugs are common exemption categories, though the specifics vary widely by state. What remains after these subtractions is your net taxable sales.
Apply the tax rate to the taxable amount. This is where combined rates matter. Most states layer a base state rate with local rates for the city, county, and sometimes a special district such as a transit authority. The applicable rate is usually based on the destination where the goods were delivered, not where your business sits. Online portals often calculate this automatically when you enter a jurisdiction code, but if you sell into dozens of locations, getting each rate right requires tax software or careful use of your state’s rate tables. A small rate error repeated across thousands of transactions creates a significant underpayment.
Then enter use tax. Report the purchase price of items your business bought without paying sales tax, apply the rate, and add the result to your balance.
The portal totals everything and shows what you owe. Some systems will show a credit instead if you overpaid in a prior period.
Submitting and Paying
Once you have reviewed every line, submit through the portal. The system generates a confirmation number. Save it somewhere outside the portal in case you lose access later. If you file on paper, use certified mail with a return receipt so you can prove the postmark date if a deadline dispute arises.
ACH bank transfer is the standard payment method and usually carries no processing fee. Portals accept credit and debit cards too, but expect a convenience fee of roughly 2% to 3% of the payment. For a business remitting thousands of dollars each month, ACH is almost always the better choice. If you mail a check, include the payment voucher from your return or your state’s website. Without the voucher, the payment may not get credited to your account on time even if the check arrives before the deadline.
If the money isn’t there, file anyway. The penalty for not filing is almost always worse than the penalty for filing without full payment. Most states offer payment plans that require monthly installments with interest continuing to accrue on the unpaid balance. Contact your state’s department of revenue before the deadline to arrange one rather than waiting for the state to reach out to you.
Claiming the Vendor Discount
Close to 30 states let businesses that file and pay on time keep a small percentage of the tax they collected. These vendor discounts, sometimes called collection allowances, typically range from 0.25% to 5% of the tax due. The discount compensates you for acting as the state’s tax collector.
Some states cap the discount at a fixed dollar amount per period, and a few scale the percentage down as collections rise. The catch is that the discount only applies when you file and pay by the deadline. Miss by a day and you forfeit the entire amount for that period. If your state offers the incentive, it’s one more argument against last-minute filing.
Fixing a Return After You File It
If you find an error after submitting, file an amended return as soon as you can. Most states allow amendments through the same portal you used to file. You select the period to correct, enter the updated figures, and provide a reason for the change. The system recalculates and either generates a balance due with interest or shows a credit.
Common reasons to amend include unreported sales you discover later, a wrong rate applied to a jurisdiction, or a resale certificate that arrives after you already reported the transaction as taxable. If the amendment produces additional tax, interest runs from the original due date. Filing a voluntary amendment generally avoids the steeper penalties that come with an audit finding. If the state owes you money, the overpayment usually applies as a credit against future returns, though you can typically request a refund for a significant amount.
What Being Late Costs
Late filing penalties typically start at 5% to 10% of the tax due for the first month, with additional charges accruing each month the return sits unfiled. Many states cap the cumulative penalty at 25% to 30% of the liability. Several states also impose flat minimum penalties from $5 to $100 regardless of the amount owed, so even a zero-balance return filed late can cost you.
Interest runs on top of penalties from the original due date, not from the date you noticed you were late. Rates vary and are often tied to the federal short-term rate plus a set number of percentage points. Interest is rarely waived even with a reasonable explanation.
Deliberately failing to remit sales tax you actually collected is a different problem. You held someone else’s money in trust, and many states classify the failure to pass it along as theft of tax funds. Federal tax evasion carries up to five years in prison and fines up to $100,000 for individuals.1Office of the Law Revision Counsel. 26 USC 7201 – Attempt to Evade or Defeat Tax State-level criminal penalties for sales tax fraud vary but can be equally severe.
How Long to Keep Everything
Most states require you to retain sales tax records for three to four years from the filing date; some extend that to six or seven. The IRS recommends keeping employment tax records for at least four years, and that’s a reasonable floor for sales tax documentation as well.2Internal Revenue Service. How Long Should I Keep Records Practically, four years covers the audit window in most states. Keep copies of every filed return, every exemption certificate, purchase invoices, and the bank statements that tie back to your reported figures.
If You Should Have Been Filing All Along
If your business has been selling into a state for years without registering or filing, a voluntary disclosure agreement is usually the least painful way to get right. The Multistate Tax Commission runs a program that lets businesses come forward anonymously through a neutral third party. The typical benefits are a waiver of all penalties and a limited look-back period of three to four years, so you would owe back taxes and interest only for that window rather than the entire noncompliant history.3Multistate Tax Commission. NNP Procedures of Multi-State Voluntary Disclosure
One exception: if you actually collected sales tax from customers but never sent it to the state, that money must be surrendered in full regardless of the look-back period. Some states also attach a small non-waivable penalty to collected-but-unremitted tax. Eligibility depends on the state not having already contacted you. Once an audit notice or inquiry letter arrives, the voluntary disclosure window closes for that state and tax type. Many states accept voluntary disclosure applications directly outside the MTC program with similar terms. Addressing exposure proactively across multiple states almost always costs less than waiting for each one to find you.