Sales tax notices are one of the most common (and stressful) surprises for growing startups. Handling sales tax correctly is a core part of startup accounting, and getting ahead of it can prevent penalties, interest, and painful clean-up work during due diligence.
So what happens? A state or local tax agency sends a letter, and suddenly your team is scrambling to figure out what you owe, which returns are missing, and whether your sales tax process is broken.
For venture-backed startups, especially SaaS and tech companies with remote employees and customers in multiple states, these notices are usually a symptom of a deeper state and local sales tax (SALT) problem, not a one-off issue.
Why startups get sales tax notices
Sales tax notices usually mean a state thinks:
- You missed a required sales, use, or excise tax return
- You underpaid or paid late
- You registered for the wrong tax type or never registered at all
- Your reported numbers do not match their data
For startups, notices often show that sales tax has not been fully integrated into the accounting and compliance stack.
Kruze’s team of startup sales tax experts reads your notice, researches it, and helps you get it fixed. We’ll also explain what happened so you can avoid similar state and local sales tax notices in the future.
Below are 10 common reasons your startup may get a sales tax notice, and how your accounting team should think about each one.
1. Failure to collect sales tax
If your startup is selling taxable products, SaaS, or services into a state where you have sales tax nexus but you are not charging customers sales tax, that state can step in and assess tax on those transactions. This often shows up as a notice assessing use tax or back sales tax, plus penalties and interest.
What this looks like:
- You are making taxable sales into a state (often online)
- Your invoices or checkout process do not include sales tax
- The state sees sales activity but no corresponding sales tax remittances
- You receive a notice asserting that tax is due on those sales
Startup accounting action:
- Run a sales tax nexus study to see where you should be collecting sales tax
- Configure your billing or invoicing system to calculate and charge sales tax correctly
- Post sales tax collected to a liability account instead of treating it as revenue
2. Payroll tax registration that creates a sales tax account
Some states, like Michigan, automatically set up additional tax accounts when you register for payroll tax. That means a startup might open a payroll account for a remote employee and unintentionally create a sales tax account at the same time.
What this looks like:
- You register in a state so you can run payroll for an employee
- The state system also opens a sales or combined tax account
- No one realizes a new account exists, so no returns are filed
- The state sends a notice requesting missing sales tax returns
Startup accounting action:
- Treat every new state payroll registration as a SALT review trigger
- Confirm which accounts (payroll, sales, excise, income, franchise) were created
- Add those accounts and due dates to your tax calendar immediately
3. Excise tax returns (for example, Washington)
In states like Washington, registering for payroll tax may automatically require excise tax returns. Many founders assume they only signed up for payroll, but the excise account (which can include B&O and sales/use tax) is active and needs filings.
What this looks like:
- You register in Washington to pay payroll tax
- The system opens an excise tax account as well
- You do not file the required excise tax returns, even when activity is zero
- Notices arrive for “missing excise tax returns”
Startup accounting action:
- Maintain a state tax matrix listing each state, account type, account number, and filing requirement
- File required zero-returns for periods with no taxable sales
- Have your CPA review any “excise” or “business and occupation” notices promptly
4. Failing to file required returns
Once your startup registers for a sales tax permit, most states expect sales tax returns on a regular schedule, even if you have no taxable sales during a period. Missing monthly, quarterly, or annual returns is one of the simplest ways to trigger a sales tax notice.
What this looks like:
- Your sales tax permit is active
- You assume that “no sales” means “no filing”
- The state expects a return every period, regardless of activity
- You receive a notice for non-filed returns, often with an estimated assessment
Startup accounting action:
- Assign a clear owner (internal or outsourced) for sales tax filings
- Build and maintain a filing calendar by state and frequency
- Reconcile each filed return to the sales tax liability account in your GL
5. Change in filing frequency
As your revenue or transaction volume grows, states may change your required filing frequency, such as from annual to quarterly, or quarterly to monthly. If you continue filing on the old schedule, the state will treat the missing periods as non-filed and send notices.
What this looks like:
- You receive a letter or online notice that your filing frequency will change
- The notice is overlooked or not routed to the right person
- You keep filing under the old schedule
- The state issues notices for missing returns at the new frequency
Startup accounting action:
- Centralize tax mail (physical and electronic) so it is reviewed promptly
- Update your tax calendar immediately when a frequency change is issued
- Confirm your tax software or provider is using the correct filing cadence
6. Failure to remit sales tax collected
Collecting sales tax from customers creates a liability – the cash belongs to the state, not the company. If your startup collects sales tax but does not remit it on time or in full, states can respond aggressively with notices, penalties, and in some cases, more serious enforcement.
What this looks like:
- Your invoices or checkout process charge sales tax
- Sales tax collected sits in your operating account
- Returns are not filed or payments are not made on time
- You receive notices about unpaid or underpaid tax, plus penalties and interest
Startup accounting action:
- Post sales tax collected to a dedicated sales tax liability account
- Reconcile that liability balance to your sales tax returns every filing period
- Schedule payments ahead of due dates and avoid using those funds for operations
7. Incorrect reporting on sales tax returns
Even when you are collecting and filing, errors in classification, rates, or data entry can lead to sales tax notices. The risk is higher for startups selling SaaS or digital products, because states differ in whether and how those items are taxed.
What this looks like:
- Some sales are incorrectly treated as exempt when they are taxable
- The wrong rate is applied due to address or sourcing errors
- Totals are transposed or mis-keyed when preparing returns
- The state’s records, third-party data, or math do not line up with your return
Startup accounting action:
- Reconcile taxable sales by state back to your invoicing and CRM systems
- Maintain documentation for exempt sales and resale certificates
- Have a knowledgeable reviewer double-check returns before filing
8. Failure to register for a sales tax permit (nexus issues)
Under modern nexus rules, your startup can owe sales tax in states where you have no physical office. Economic nexus laws (post-Wayfair) often require remote sellers to register once they cross a state’s revenue or transaction thresholds, even for purely online sales.
What this looks like:
- You are selling into a state and exceed its economic nexus thresholds
- You have remote employees, contractors, or inventory in a state
- You never register for a sales tax permit in that state
- The state discovers your activity and issues a notice
Startup accounting action:
- Run a nexus review at least annually and after major growth or hiring
- Register proactively in states where you have established nexus
- Align registration dates and compliance with when business activity began
9. Underreporting taxable sales or transactions
States compare what you report to their own data sources, including marketplace reports, 1099‑K information, and industry benchmarks. If your reported taxable sales look too low relative to those data points, a notice or audit inquiry is likely.
What this looks like:
- You have significant sales through marketplaces, app stores, or payment processors
- States receive third-party data suggesting higher sales than you report
- Exemptions or misclassification make your taxable base appear unusually small
- The state sends a notice asking for support or assessing additional tax
Startup accounting action:
- Maintain detailed sales records by state, product, and channel (direct vs. marketplace)
- Work with a startup-focused CPA to classify sales and exemptions correctly
- Document how marketplace facilitator rules apply to your model
10. Late filing or late payments of sales tax returns
Sometimes the issue is simply timing. Filing or paying even a few days late can generate automated penalty and interest notices. Repeat lateness can increase penalty rates and draw more scrutiny from state tax authorities.
What this looks like:
- Returns are prepared at the last minute and miss the cutoff
- Payments hit the bank a day or two after the due date
- Notices arrive assessing penalties and interest, even if tax was ultimately paid
- Over time, the pattern can lead to additional follow-up or audits
Startup accounting action:
- Automate reminders and workflows ahead of due dates
- Give your accounting team or provider sufficient lead time before deadlines
- Consider outsourced sales tax compliance if volume or complexity is growing
Integrating sales tax into your startup accounting stack
To reduce sales tax notices and keep state and local compliance under control, build sales tax into your core startup accounting workflows.
Key touchpoints:
- State registrations
- Track each state where you are registered and which tax accounts are open
- Revenue and billing systems
- Configure tax rules in your invoicing or billing platform to apply correct rates
- CRM and sales operations
- Capture accurate customer locations and monitor sales by state for nexus
- Monthly close
- Reconcile sales tax liabilities and filed returns as part of your close checklist
When sales tax is managed as part of your normal accounting process, notices become rare exceptions instead of a constant distraction.
When to bring in a startup tax specialist
Because every state (and many local jurisdictions) has its own rules, early-stage companies often benefit from working with a CPA firm that specializes in VC-backed startups once they begin generating meaningful revenue or hiring remotely.
A startup-focused sales tax team can:
- Map where you have nexus and identify required registrations
- Set up and manage a multi-state sales tax filing calendar
- Respond to and resolve sales tax notices, including back filings or voluntary disclosures
- Align sales tax treatment with revenue recognition and investor-ready financials
Got a sales tax notice? Kruze’s Sales Tax Team is here to support you, so you can get back to building your product and serving customers.