How to Pay Connecticut Small Business Taxes in 2026

Running a business in Connecticut means handling more than just sales, customers, and payroll. It also means knowing which state taxes apply, when they are due, and which agency expects each filing. The good news is that Connecticut uses a mostly digital system, so once your registrations are set up, staying compliant is much easier to manage.

This guide walks through the main Connecticut small business taxes, who usually owes them, where to file, and the deadlines that matter most in 2026.

The main Connecticut business taxes to know

Most small businesses in Connecticut may deal with one or more of these tax categories:

• Corporation business tax for C corporations and certain corporations with Connecticut nexus
• Pass-through entity tax for eligible partnerships, S corporations, and LLCs taxed as partnerships
• Sales and use tax for businesses selling taxable goods or services, or making taxable business purchases without paying Connecticut tax at checkout
• Income tax withholding for employers
• Unemployment insurance tax for employers, which is handled through the Connecticut Department of Labor

Not every business owes every tax. Your entity type, activities, employees, and sales determine what applies.

Start with registration

Before filing any state business tax return, register your business with the Connecticut Department of Revenue Services through myconneCT. Connecticut requires new businesses to complete Form REG-1 electronically.

myconneCT is the state’s online portal for:

• Registering a new business
• Filing returns
• Making payments
• Viewing filing history
• Sending secure messages to DRS

If you are still in the formation stage, this is also a good time to make sure your entity records, EIN, ownership documents, and state registrations are organized. Clean records make tax filing much simpler later.

1. Corporation business tax

Connecticut imposes the corporation business tax on C corporations and on some corporations that carry on business in the state or have the right to do business here. A corporation with substantial economic presence in Connecticut may also have a filing obligation.

How the tax works

Connecticut corporate tax liability is based on the greater of two calculations:

• Net income base tax, which uses a 7.5% rate
• Capital base tax, which uses a 0.21% rate and cannot be less than $250

In practice, corporations usually need to evaluate both computations and pay the higher amount.

When the return is due

For most calendar-year corporations, the return is due on May 15, which is the 15th day of the fifth month after the federal due date.

If a corporation has a June 30 year-end, the return is generally due on October 15.

Estimated payments

Corporations may also need estimated tax payments during the year. If estimated tax applies, it is generally paid in four installments during the tax year.

Filing method

All corporation business tax returns must be filed electronically.

2. Pass-through entity tax

Connecticut’s pass-through entity tax is optional, but the election is important because once an eligible entity elects to pay it, the election is irrevocable for that year.

This tax is generally relevant to:

• Partnerships
• S corporations
• LLCs treated as partnerships for federal income tax purposes

Why it matters

The PE tax can help eligible entities manage Connecticut tax at the entity level instead of leaving the entire burden to the owners. That makes it a key planning item for many multi-owner businesses.

Due date

Form CT-PET is due on the 15th day of the third month after the close of the taxable year.

For calendar-year filers, that means March 15.

Estimated payments

If the required annual payment is $1,000 or more, estimated payments are made in four installments:

• April 15 for calendar-year filers
• June 15 for calendar-year filers
• September 15 for calendar-year filers
• January 15 for calendar-year filers

Filing method

Form CT-PET, extension requests, and estimated payments must be filed and paid electronically through myconneCT or the IRS Modernized e-File program.

3. Sales and use tax

If your business sells taxable goods or taxable services in Connecticut, sales and use tax is one of the most common obligations.

The general rate

Connecticut’s general sales and use tax rate is 6.35%.

There are no additional local sales taxes in Connecticut, so the statewide rate is the rate most businesses use for taxable sales.

Special rates

Some sales qualify for different rates, including:

• 1% for certain computer and data processing services
• 2.99% for certain vessel-related sales and dyed diesel fuel sold for marine purposes
• 4.5% for certain motor vehicle sales to qualifying nonresident military personnel
• 7.35% for meals and certain beverages
• 7.75% for certain high-value vehicles, jewelry, and qualifying clothing or accessories
• 9.35% for short-term rentals or leases of passenger motor vehicles

Filing and payment

Form OS-114 must be filed and paid electronically through myconneCT.

A business must file its sales and use tax return even if no sales were made or no tax is due.

Due date

The return is due on or before the last day of the month following the end of the filing period.

Business use tax

If your business buys taxable items for use in Connecticut and the seller does not charge Connecticut sales tax, you may owe use tax instead. This is common when businesses buy equipment, supplies, or software from out-of-state sellers.

4. Withholding tax

If you have employees, Connecticut withholding tax is usually part of your compliance calendar.

Who needs to register

Employers that are not already registered with DRS must register for Connecticut income tax withholding.

How it is filed

Connecticut requires withholding tax filings and payments to be made electronically.

Common reconciliation forms

• Form CT-941 for quarterly withholding reconciliation
• Form CT-W3 for annual reconciliation with Forms W-2

Key due dates

• Quarterly CT-941 returns are due on the last day of the month following the quarter
• CT-W3 and W-2 forms are due by January 31

Important note for employers

Connecticut does not use a single flat withholding rate for every employer in the same way some people expect. Withholding is based on employee-level calculations and the state’s withholding tables and rules.

5. Unemployment insurance tax

Unemployment insurance tax is separate from DRS-administered taxes and is handled through the Connecticut Department of Labor.

2026 rates and wage base

For 2026, Connecticut uses:

• A taxable wage base of $27,000
• A new employer rate of 1.9%
• A rate range of 1.1% to 9.9%

Why this matters

If you have employees, this tax can be one of your larger recurring payroll obligations. The rate you pay depends on employer classification and experience rating.

A practical filing calendar for Connecticut businesses

If you want to stay ahead of deadlines, build your calendar around these recurring checkpoints:

• May 15: Calendar-year corporation business tax return
• March 15: Calendar-year pass-through entity tax return
• April 15, June 15, September 15, and January 15: PE tax estimated payments, if required
• Last day of the month after each filing period: sales and use tax returns
• Last day of the month after each quarter: quarterly withholding returns
• January 31: Annual withholding reconciliation and W-2 reporting

Your exact schedule may differ based on entity type, filing frequency, and DRS account setup, so confirm the due dates assigned to your business.

Records you should keep

Good tax filing starts with good recordkeeping. At a minimum, keep these items organized:

• EIN and Connecticut Tax Registration Number
• Formation documents
• Prior-year returns
• Sales reports
• Invoices and receipts
• Payroll records
• Bank statements
• Proof of estimated payments
• Copies of filed state returns and confirmations

If you manage all of this in one place, filing becomes much faster and far less stressful.

Common mistakes to avoid

The most avoidable Connecticut tax problems usually come from a few simple errors:

• Failing to register for the right tax accounts before you start operating
• Missing electronic filing requirements
• Ignoring sales tax on taxable items or services
• Forgetting to file zero returns when required
• Mixing up DRS obligations with Department of Labor obligations
• Missing estimated payments or reconciliation deadlines

A short review each quarter usually prevents bigger problems later.

How Zenind fits in

If you are forming a Connecticut LLC or corporation, Zenind can help you stay organized from the beginning by keeping formation documents and compliance milestones in order. That kind of structure makes tax prep easier when filing season arrives.

For many business owners, tax compliance is not really about doing everything at once. It is about putting the right records, registrations, and deadlines in place early so the rest of the year runs smoothly.

Conclusion

Connecticut small business taxes are manageable when you know which agency handles each obligation and which deadlines apply to your business. Register through myconneCT, identify the taxes tied to your entity type, file electronically, and keep your records clean throughout the year.

If you handle the basics early, Connecticut tax compliance becomes a routine part of running the business rather than an emergency at year-end.