"Crossed a Sales Tax Threshold? Registration, Voluntary Disclosure and Back-Tax Exposure"

10/12/2026

Discovering that a client has crossed a state's economic nexus threshold is the start of the work, not the end. What happens next determines whether the client pays only the tax it should have collected or pays that tax plus penalties, interest and the cost of a full audit. The difference usually comes down to the order in which things are done.

The instinctive move is to go to the state's website and register immediately. Sometimes that is right. Often it is the most expensive possible first step, because registering can disclose the business to the state before the client has considered the program designed to limit past exposure. This post sets out the after-nexus workflow in the order that protects the client: measure, decide on disclosure, register, set up filing, and manage the obligation over time, including what happens if sales drop back below the threshold.

Thresholds, lookback periods, filing frequencies and program terms are set by each state and change, so this post describes the mechanisms and the decisions. For any specific state, confirm the current rules with its revenue department.

Step 1: Pin Down When Nexus Started

Exposure runs from the date the obligation began, so the first job is to establish that date for each state.

Measure on the state's terms. States differ on whether the threshold measures gross, retail or taxable sales, whether a transaction-count test applies, and whether the measurement period is the previous calendar year, the current calendar year or a rolling twelve months. Also check whether marketplace-facilitated sales count toward the threshold for the client's direct sales.
Find the crossing date. Identify the transaction that took the client over the threshold and the date from which the state requires collection. Some states require collection from the next transaction; others from the start of a following month or period. The statute or guidance will say.
Look for physical presence too. Inventory in a fulfillment warehouse, remote employees, contractors, trade show sales and property in the state can create nexus earlier than any economic threshold. If the client had physical presence, the start date may predate the threshold crossing entirely.

Our post on sales and use tax nexus rules covers how each of these triggers works.

Step 2: Quantify the Back-Tax Exposure

Before contacting any state, estimate what is owed for each state from the start date to today.

Taxable sales. Not all sales into the state are taxable. Remove exempt products and services and sales to exempt buyers, but only where the client holds valid exemption certificates. Missing certificates mean the sale is treated as taxable until proven otherwise.
Facilitated sales. Remove sales on which a marketplace facilitator collected tax.
Apply the combined state and local rate for each delivery location. Rough averages are fine for an estimate; returns will need exact rates.
Tax collected. Note any tax the client actually collected from customers but did not remit. This is treated more seriously than tax never collected, and many states and disclosure programs require all of it to be paid regardless of the lookback period.
Interest and penalties. Estimate both for the full period, so the cost of doing nothing can be compared with the cost of coming forward.
Use tax. While you are at it, look at the client's own untaxed purchases in each state; use tax exposure is often found during the same review.

The exposure is the tax the client should have collected, whether or not it did. Sellers are liable for uncollected tax, and going back to customers years later to collect it is rarely practical. That is why speed matters once nexus is identified: every month of delay adds tax that will come out of the client's own margin.

Step 3: Decide Whether to Use a Voluntary Disclosure Agreement

What a VDA is

Most states with a sales tax offer a voluntary disclosure agreement (VDA) program. In exchange for coming forward before the state contacts it, registering, filing returns and paying the tax for a defined lookback period, the taxpayer typically receives:

A limited lookback. The state does not pursue tax for periods before the lookback. Under the Multistate Tax Commission's multistate program, lookback periods are usually three or four years, set by each participating state. Individual state programs set their own.
Penalty waiver for the lookback period, in most cases.
Interest, however, is generally still due. The Multistate Tax Commission's program states that interest is due on the lookback-period liability unless the state expressly waives it.
Anonymity during negotiation. Most programs allow the taxpayer to be represented anonymously, usually through its accountant or attorney, until the agreement is signed.

Eligibility is the critical issue

VDA programs are generally open only to taxpayers the state has not already contacted about the tax. The Multistate Tax Commission's program states that prior contact between a state and a taxpayer about a tax type disqualifies the taxpayer for that tax type, and it counts filing a return, paying the tax, or receiving an inquiry from the state as contact. State programs have their own wording, but the principle is common.

That is why registering first can be costly. Once the client registers, the state knows it exists, and in many states the client may no longer qualify for the VDA terms. The state can then pursue the full period, potentially back to the start of nexus, with penalties. If no return was ever filed, the normal assessment period may not have begun to run, so "the full period" can be long.

When a VDA makes sense

Exposure is material relative to the cost of the process.
The nexus start date is more than a short time ago, so the lookback limit actually saves something.
The client has not been contacted and has not registered or filed in the state.
The client wants penalty relief and certainty.

When it may not

Exposure is small or very recent, so the lookback saves little and the process cost exceeds the benefit.
The client is already registered or has been contacted.
The state offers a different route that fits better, such as an amnesty or a simplified registration program.

Multistate disclosure

The Multistate Tax Commission's Multistate Voluntary Disclosure Program lets a taxpayer approach several participating states through one process, with a uniform procedure. Each state still sets its own lookback and terms and signs its own agreement. For a client with exposure in many states it is worth considering alongside direct state-by-state VDAs.

Step 4: Register

Once the disclosure decision is made, the client registers in each state where it has nexus, either as part of the VDA or directly.

What registration involves

Applying for a sales tax permit (also called a seller's permit, license or certificate, depending on the state) through the state's online portal.
Providing entity details, ownership, federal employer identification number, business activity, products sold and the date sales into the state began.
Choosing or being assigned a filing frequency.
In some states, paying a fee or posting a bond.

Answer the "date business began in the state" question accurately and with the disclosure decision already made. This date is effectively an admission of the start of the obligation.

Streamlined Sales Tax registration

About two dozen states are members of the Streamlined Sales and Use Tax Agreement. The Streamlined Sales Tax Registration System (SSTRS) lets a seller register in any of those member states through a single application, selecting only the states where it has nexus. There is no fee to register through SSTRS itself, although a state may charge a fee where its law requires one. Sellers that want to use a Certified Service Provider, which can handle calculation and filing, must register through SSTRS.

Two cautions from the SST guidance:

Registering through SSTRS does not relieve a seller of liability for prior sales except where a state offers amnesty.
SST amnesty is narrow. According to the Streamlined Sales Tax site, Tennessee is currently the only state offering it; it is not available to a seller that was registered in the state during the twelve months before the state's participation date; and the seller must remain registered and collecting for at least 36 months. Check the current terms before relying on it.

For non-member states, register directly with each state.

Step 5: Set Up Collection and Filing

Filing frequency

States assign filing frequency, usually monthly, quarterly or annually, based mostly on the volume of tax the seller collects or expects to collect. New registrants are often assigned a frequency based on estimates and moved later. Some states also require prepayments or accelerated payments for large filers. Record each state's frequency and due date in the firm's filing calendar; due dates and weekend rules differ by state.

Collection setup

Configure the client's checkout, invoicing or tax engine to charge the right rate for each delivery address from the registration effective date.
Set taxability rules for each product in each state.
Set up exemption certificate collection and storage for exempt buyers, with expiration tracking.
Make sure marketplace-facilitated sales are reported correctly on returns where the state requires them.

Zero returns

A registered seller generally must file every return, even when no tax is due. Missing zero returns produces non-filing notices, penalties and sometimes estimated assessments. Build them into the calendar.

Reconciliation

Each period, reconcile tax collected per the sales system, tax per the general ledger liability account and tax reported on returns. Differences caught monthly are small; differences caught on audit are not.

Step 6: Manage Trailing Nexus and Deregistration

Sales fall. A product line ends, a channel is closed, a big customer leaves. Falling below a state's threshold does not necessarily end the obligation.

Trailing nexus describes the period after a seller drops below the threshold, or ends physical presence, during which some states still require it to collect. States that measure the threshold on the previous calendar year effectively build in a trailing period: a seller over the threshold last year must collect for this year even if this year's sales are lower. Some states also have explicit rules continuing nexus for a set period after physical presence ends. Others say little about it.

Before deregistering:

Confirm the state's rule for when the obligation ends.
Confirm the measurement period has actually run past the threshold.
File final returns and request account closure in the state's required form.
Keep registration where the client is likely to cross the threshold again soon; deregistering and re-registering creates gaps and administrative cost.

Deregistering too early creates a gap period of uncollected tax, which is exactly the exposure the whole process was designed to fix.

Step 7: Keep Monitoring

Nexus is not a one-time determination. Thresholds change, states amend counting rules, and the client's sales mix moves. Set a monitoring routine:

Track sales by state monthly against each threshold, using each state's own measure.
Track inventory locations from fulfillment programs.
Track remote employees and contractors by state.
Recheck threshold rules for each active state at least annually.

Tools can automate tracking; our post on AI for sales and use tax compliance covers what they do well and where they still need review. Remote staff create payroll obligations that are usually discovered at the same time; see multi-state payroll withholding.

The After-Nexus Sequence on One Page

Step	Question to answer	Common mistake
1. Start date	When did the obligation begin in each state?	Measuring on the wrong sales definition
2. Exposure	What is owed, with interest and penalties?	Forgetting tax collected but not remitted
3. Disclosure	Is a VDA worth it, and is the client eligible?	Registering first and losing eligibility
4. Register	Directly, via VDA, or through SSTRS?	Careless start date on the application
5. File	Frequency, due dates, zero returns, reconciliation	Missing zero returns
6. Trailing nexus	When does the obligation end?	Deregistering too early
7. Monitor	Are new states approaching thresholds?	Treating nexus as a one-time study

Training on Sales and Use Tax Determinations

Each of these steps depends on accurate determinations: which sales count, which are taxable, and where. The Relieving Sales and Use Tax Determination Headaches webinar is built around making those sales and use tax determinations. Our broader sales and use tax training catalog and sales and use tax FAQs cover the surrounding topics.

Frequently Asked Questions

What should I do first after crossing a sales tax threshold?

Establish when the obligation started in each state and estimate the tax that should have been collected since then, before contacting the state. That estimate tells you whether a voluntary disclosure agreement is worth pursuing. If exposure is very recent and small, registering directly may be simplest. If it is material and older, registering first can cost the client eligibility for a program that limits the lookback period and waives penalties.

Can registering for sales tax disqualify a business from voluntary disclosure?

It can. Voluntary disclosure programs are generally limited to taxpayers the state has not already contacted about the tax. The Multistate Tax Commission's program, for example, treats filing a return, paying tax or receiving a state inquiry as prior contact that disqualifies the taxpayer for that tax type. Individual state programs use their own wording, so check eligibility for each state before registering if there is meaningful past exposure.

How far back does a sales tax voluntary disclosure agreement go?

Each state sets its own lookback period. Under the Multistate Tax Commission's multistate program, lookback periods are usually three or four years, and state programs often fall in a similar range. Tax actually collected from customers but not remitted may be required for the full period regardless. Penalties are typically waived for the lookback period, but interest is generally still due unless the state agrees otherwise.

What is the Streamlined Sales Tax Registration System?

SSTRS is a central registration system for the roughly two dozen states that are members of the Streamlined Sales and Use Tax Agreement. A seller can register in any member states where it has nexus through one application, with no fee charged by SSTRS itself. Registering through SSTRS does not relieve liability for past sales, except under the narrow amnesty some member states have offered, so past exposure still has to be addressed.

How is sales tax filing frequency determined?

The state assigns it, usually monthly, quarterly or annually, based mainly on how much tax the seller collects or is expected to collect. New registrants are often placed on a frequency based on their estimate and moved later as actual volume becomes clear. Some states require prepayments from large filers. Every assigned return must be filed, including zero returns for periods with no taxable sales.

What is trailing nexus?

Trailing nexus is a continuing obligation to collect sales tax for a period after a seller falls below a state's economic threshold or ends its physical presence there. States that measure thresholds on the previous calendar year effectively create one automatically, and some states have explicit trailing rules for physical presence. Before deregistering, confirm the state's rule and file final returns properly, because deregistering too early leaves a period of uncollected tax.