Connecticut Sales Tax Nexus: Thresholds & CPA Steps

Introduction

Connecticut sales tax nexus rules are relatively streamlined compared to many states, yet they carry meaningful compliance risk for remote sellers due to dual economic nexus thresholds and aggressive enforcement. For CPA firms advising ecommerce businesses, SaaS providers, and multistate operators, Connecticut requires disciplined monitoring of both revenue and transaction volume.

Connecticut adopted economic nexus shortly after the Wayfair decision and applies marketplace facilitator rules broadly. This guide outlines how nexus is created in Connecticut, applicable thresholds, registration and filing obligations, and CPA-level action steps.

What Creates Sales Tax Nexus in Connecticut?

Physical Nexus

Physical presence includes:

• Offices, warehouses, or retail locations

• Inventory stored in Connecticut

• Employees or contractors working in the state

• Installation or service activity performed in-state

Physical nexus creates immediate collection obligations.

Economic Nexus

Remote sellers may establish nexus based on sales activity alone, even without physical presence.

Affiliate and Marketplace Nexus

Affiliate relationships and marketplace sales can create or shift collection responsibility depending on the facts.

Economic Nexus Thresholds in Connecticut

Connecticut applies both revenue and transaction thresholds.

A seller establishes economic nexus if it has, during the previous or current 12-month period:

• More than $100,000 in gross Connecticut sales, and

• 200 or more separate transactions

Both thresholds must be met.

CPA Notes

• Gross sales include taxable and exempt transactions

• Thresholds are measured on a rolling 12-month basis

• Once exceeded, registration is required promptly

Does Connecticut Impose Sales Tax?

Yes. Connecticut imposes a state-administered sales and use tax. There are no local sales taxes, which simplifies rate determination and filing.

Registration Requirements After Nexus Is Established

Registration is completed with the Connecticut Department of Revenue Services.

• Registration should occur as soon as nexus is established

• Collection begins prospectively after registration

• Marketplace sellers may still need registration for non-marketplace sales

Filing Frequency and Due Dates

• Monthly filing is standard

• Returns are due by the last day of the month following the reporting period

• Electronic filing is required

Penalties and Interest

Connecticut imposes penalties for:

• Late filing

• Late payment

• Underpayment due to negligence

Interest accrues from the original due date.

CPA Action Steps for Connecticut Nexus Reviews

1. Monitor rolling 12-month sales and transaction counts

2. Confirm physical presence triggers

3. Review marketplace facilitator coverage

4. Register promptly once both thresholds are met

5. Maintain audit-ready documentation

Common CPA Mistakes

• Tracking revenue but ignoring transaction counts

• Assuming marketplace collection eliminates all obligations

• Delaying registration after thresholds are exceeded

FAQs

Does Connecticut use a revenue-only threshold?
No. Both revenue and transaction thresholds apply.

Are exempt sales included?
Yes, for nexus determination.

Conclusion

Connecticut sales tax nexus rules are clear but strict. CPA firms must track both revenue and transaction volume carefully to ensure timely compliance and avoid penalties.