Connecticut Manufacturing Sales Tax Exemption: Who Qualifies

Connecticut’s manufacturing sales tax exemption lets qualifying manufacturers buy machinery, materials, tools, and fuel used directly in production without paying the state’s 6.35% sales and use tax, and it offers a 50% partial exemption for a broader range of production-related purchases that fall short of the “used directly” standard.¹ To claim either exemption, your facility has to meet the state’s definition of a manufacturing plant, you have to present the correct exemption certificate to each vendor, and you have to keep records that will survive an audit.

Who Counts as a Manufacturer

Making things isn’t enough on its own. Connecticut defines a “manufacturing plant” as an establishment whose predominant purpose is manufacturing and that is generally recognized as such.² The Department of Revenue Services (DRS) applies a four-factor test to decide whether manufacturing predominates at your site:

Floor space devoted to production rather than to offices, warehousing, or retail.
Headcount of workers actually engaged in production.
Payroll attributable to production workers.
Operating costs tied to manufacturing activity.

DRS weighs these together rather than applying a single rigid cutoff, though “predominant” generally tracks to more than 50%. Research and development counts on the manufacturing side of each factor, so a plant with a large R&D wing doesn’t lose eligibility because of that space.²

A few situations disqualify a business outright. Cottage industries do not qualify: if you manufacture in a residential dwelling or on residential property, the establishment is not a manufacturing plant, no matter how much you produce. Locations sitting outside commercial or industrial zoning are less likely to qualify. And if a site mostly sells goods manufactured elsewhere, the DRS is likely to treat it as retail rather than manufacturing.²

What Purchases Are Fully Exempt

Two statutes carry the full exemption, and they cover different categories of purchases.

Machinery Used Directly in Production

Under C.G.S. § 12-412(34), machinery used directly in a manufacturing production process is fully exempt. Connecticut reads “machinery” broadly: the exemption covers the basic machine, all component parts and contrivances used to control, regulate, or operate it, and all replacement and repair parts, whether purchased together or separately.³ Machinery used exclusively to monitor or control a manufacturing activity is covered, and so is equipment used exclusively during production to test or measure the materials and products being made.

Office equipment and general data processing equipment do not qualify. The one exception is numerically controlled machinery used directly in production.³

A companion provision, C.G.S. § 12-412(73), fully exempts component parts purchased to be assembled into machinery that will be used directly in manufacturing, even if the finished machine hasn’t yet gone into production.¹ If you’re building a custom production line out of purchased components, each part qualifies for the full exemption on its own.

Materials, Tools, and Fuel

Under C.G.S. § 12-412(18), materials, tools, and fuel used directly in an industrial plant to fabricate a finished product for sale are fully exempt.³ The exemption also covers materials and fuel used to furnish power to a manufacturing plant, and to deliver gas, water, steam, or electricity to consumers through mains, lines, or pipes.

The operative words are “used directly.” Items that become part of the finished product qualify without question, and so do consumables burned up during production — grinding wheels, lubricants, chemical reagents. Items with a general facility purpose, like cleaning supplies for the office, don’t qualify.⁴ Most audit fights in this category turn on the distinction between things used in the plant and things used directly in fabrication, so document the specific role each item plays on the line.

Gas and Electricity: The 75% Rule

Gas and electricity used in manufacturing are fully exempt under C.G.S. § 12-412(3), but only when at least 75% of the gas or electricity consumed at the metered building, location, or premises goes to production, fabrication, or manufacturing.³ Fall below 75% at a given meter and the entire exemption for that meter is lost. There is no prorated benefit.

Claiming this exemption typically calls for a utility study that inventories every piece of equipment drawing gas or electricity at the metered location and calculates annual consumption for each. Both production and non-production loads have to be cataloged. A study that misclassifies equipment or miscounts usage can lead DRS to deny the exemption outright. Where production and administrative functions share space, separate metering for the production area is often the cleanest way to clear the 75% threshold.

The 50% Partial Exemption

Purchases that can’t meet the strict “used directly” standard may still qualify for a 50% reduction in taxable gross receipts under the Manufacturing Recovery Act, codified at C.G.S. § 12-412i.⁵ Rather than paying tax on the full purchase price, you pay tax on only half of it, which brings the effective rate to about 3.18%.

The MRA reaches machinery and equipment used primarily — not necessarily directly — in manufacturing, processing, or fabricating. It specifically covers equipment used for research and development and for measuring or testing in connection with the production process.⁵ Quality control instruments, R&D lab equipment, and testing devices that support the production line without directly operating on it are the most common candidates. DRS has described the MRA as available to a broader range of property than the full exemptions in § 12-412(18) and (34).⁶

The practical approach: evaluate a purchase against the full exemption first, and fall back to the MRA partial exemption only when the “used directly” test can’t be met.

Claiming the Exemption: Certificates and Vendors

You claim either exemption by presenting the correct certificate to each vendor at the time of purchase. Two forms do most of the work:

CERT-100 for materials, tools, and fuel used directly in an industrial manufacturing plant to fabricate products for sale, or to furnish power to the plant.⁷
CERT-101 for machinery, component parts, and replacement or repair parts used directly in a manufacturing production process.⁸

Both are on the DRS website.⁹ Each certificate needs your Connecticut Tax Registration Number, a description of the property being purchased, and a declaration of how it will be used. The intended-use statement is the piece that draws audit attention, so be specific about the production process the equipment or materials will serve. Vague descriptions invite challenges.

A certificate can cover a single transaction or run as a blanket certificate for a continuing line of similar purchases from the same vendor. Blanket certificates must be renewed at least every three years.¹⁰ Recurring purchases from a regular supplier are a natural fit for a blanket certificate; one-off capital equipment orders are fine on a single-transaction form.

When a vendor accepts a properly completed certificate in good faith, they are relieved of the obligation to collect sales tax on that sale. The burden of proving that the sale actually qualifies for the exemption then rests on you as the purchaser.¹¹

Recordkeeping and Recovering Tax Paid in Error

Both you and the vendor need to keep every signed certificate. Connecticut’s general record retention rule requires tax records to be preserved for at least three years from the extended due date of the return.¹² DRS can reach further back in cases involving fraud or substantial understatement, and most tax professionals recommend holding records for at least six years as a practical safeguard.

If a vendor refuses to honor a valid certificate or charges sales tax on a qualifying purchase by mistake, you can recover the tax through the DRS refund process. Form AU-524 (Assignment of Retailer’s Rights for Refund) has to be signed by the vendor confirming they collected the tax, remitted it to DRS, and waive their own right to claim a refund of the same amount. Submit proof of payment and copies of the original invoices with it. If you self-assessed use tax on a purchase that should have been exempt, and never paid tax to a retailer, you can file a refund claim directly without the AU-524 assignment.¹³ Incomplete certificates or missing invoices will sink a refund claim.

Audit Risk and Penalties

Connecticut treats false exemption certificates seriously. Willfully delivering a false return or certificate to DRS can bring a fine of up to $5,000, imprisonment for up to five years, or both. On top of any criminal exposure, DRS will assess the unpaid tax plus interest and civil penalties on purchases where an exemption was improperly claimed.

Outright fraud isn’t the usual problem. Sloppy classification is. A manufacturer buys equipment believing it qualifies for the full exemption under § 12-412(34), the equipment ends up in a quality-control lab rather than on the production floor, and DRS reclassifies the purchase on audit as eligible only for the 50% MRA rate. The business then owes the difference plus interest going back years. If the equipment doesn’t meet even the MRA’s broader standard, the full 6.35% becomes due.¹⁴

To keep audit exposure down, document how each exempt purchase connects to a specific production process. Keep a log showing where machinery physically sits and what it does. When a piece of equipment serves both production and non-production uses, claim the partial exemption rather than the full one. The cost of being wrong about a full exemption tends to outweigh the incremental tax savings.

1
Connecticut State Department of Revenue Services. IP 2009(13) Sales and Use Taxes Guide for Manufacturers, Fabricators and Processors
2
Connecticut eRegulations. Connecticut Regulations Section 12-412(34)-1 – Machinery Used Directly in a Manufacturing Production Process
3
Justia. Connecticut Code 12-412 – Exemptions
4
Connecticut eRegulations. Connecticut Regulations Section 12-412(18)-1
5
Justia. Connecticut Code 12-412i – Partial Exemption for Materials, Tools, Fuels, Machinery and Equipment Used in Manufacturing
6
Connecticut State Department of Revenue Services. SN 93(1.1) The Manufacturing Recovery Act of 1992 Exemption for Purchases of Property Used in Manufacturing, Processing and Fabricating
7
Connecticut Department of Revenue Services. CERT-100 – Materials, Tools, and Fuel
8
Department of Revenue Services. CERT-101 – Machinery, Component Parts, and Replacement and Repair Parts of Machinery Used Directly in a Manufacturing Process
9
Connecticut State Department of Revenue Services. Exemption Certificates
10
Connecticut State Department of Revenue Services. IP 2009(15) Notice to Retailers on Sales and Use Tax Resale Certificates
11
Connecticut General Assembly. Connecticut General Statutes Chapter 219 – Sales and Use Taxes
12
Connecticut eRegulations. Connecticut Regulations Section 12-2-12 – Recordkeeping and Record Retention
13
Connecticut State Department of Revenue Services. PS 98(5) Sales and Use Tax Refund Policy
14
Connecticut State Department of Revenue Services. Sales and Use Tax Information