Do You Pay Sales Tax on a Mini Split Installation in NYC?

No, a properly contracted ductless mini split installation in New York City is generally exempt from sales tax, provided the work qualifies as a capital improvement and you give your contractor a completed Form ST-124 (Certificate of Capital Improvement). With NYC’s combined sales tax rate of 8.875%, that exemption is worth roughly $450 to $1,300 on a typical $5,000–$15,000 install. The sales tax on mini split installation NYC question trips up homeowners because two separate exemptions exist and most contractors don’t explain either one.

What Is the Capital Improvement Test for a Mini Split?

New York State requires a job to pass all three of the following tests before it qualifies as a capital improvement (per NY TB-ST-113 and Publication 862):

• Value or life test: The work must substantially add to the value of the property or appreciably prolong its useful life.
• Permanence test: The improvement must become part of, or be permanently affixed to, the real property, so that removing it would cause material damage.
• Intent test: The installation must be intended as a permanent installation, not a temporary or removable one.

A ductless mini split system clears all three. The outdoor condenser is bolted to a bracket or pad, refrigerant line sets are routed through a cored hole in the wall, and the indoor head units are wall- or ceiling-mounted with wiring run to a dedicated circuit. Pulling the system out would leave holes in the masonry, severed wiring, and a patched wall, classic material damage. A freestanding window AC, by contrast, does not qualify: it is designed to be removed without damage.

How Does Form ST-124 Actually Work?

Form ST-124 is the New York State Certificate of Capital Improvement. Here is what each party does:

• You (the property owner) fill out and sign the form, describing the work and the property address. Only the property owner or an authorized officer of the owning entity can sign, a tenant signature produces an invalid certificate.
• Your contractor keeps the signed original as proof that the job is tax-exempt.
• You must provide the form within 90 days after the service is rendered. Miss that window and the contractor is legally required to collect sales tax on the full contract amount.

Critically, the form does not let you buy equipment or materials tax-free. On a capital-improvement job the contractor is treated as the final consumer of the materials (the outdoor unit, indoor heads, line set, refrigerant). The contractor pays sales tax at the supply house, absorbs it, and builds it into their price. You will not see a “sales tax” line on your invoice for a properly billed capital-improvement install, that absence is correct, not an error.

ST-124 vs. TP-385: Two Exemptions NYC Homeowners Confuse

Out-of-state equipment retailers and some HVAC websites loosely claim “HVAC equipment is sales-tax exempt in New York.” That claim refers to a completely different rule. Here is how the two exemptions compare:

Bottom line: ST-124 is about the install; TP-385 is about the electricity that runs the system afterward. You can benefit from both, but they solve different problems.

What Does the Exemption Save on a Real NYC Mini Split Quote?

NYC’s combined rate is 4% state + 4.5% city + 0.375% MCTD = 8.875%. Apply that to common install scenarios:

These savings are entirely separate from any Con Edison Clean Heat or EmPower+ rebates you may stack on top.

Co-op and Condo Buildings: Who Signs the ST-124?

NYC’s co-op and condo stock adds a wrinkle. The rule is simple: the owner of the real property signs. In practice:

• Condo unit owner contracting work inside their unit: the unit owner signs.
• Co-op shareholder: the co-op corporation owns the real property, so strictly speaking the board or managing agent should sign for work affecting the building’s real property (e.g., exterior penetrations, common elements). For purely interior work contracted directly by the shareholder, consult your managing agent. An invalid signer exposes the contractor to a full tax assessment.
• Mixed-use building: the building owner or managing agent signs. The separate TP-385 energy exemption may also apply if residential use predominates, but that is a utility-billing question, not an installation one.

If your co-op board is already involved in approving your install, ask them to countersign the ST-124 at the same time to avoid chasing signatures later. For more on navigating the board process, see our guide on mini split installation COI requirements for NYC co-op and condo boards.

The Repair-vs-Installation Trap for Mini Splits

Repair and maintenance work is the opposite of a capital improvement: it is taxable in New York, and sales tax applies to the entire bill (labor plus materials). This creates a specific trap for mini split owners:

• Original installation of a new ductless system: capital improvement, ST-124 applies, no sales tax on the service.
• Annual maintenance visit (filter cleaning, coil wash, refrigerant check): taxable, you will owe sales tax on that invoice.
• Non-upgrade repair (replacing a failed fan motor, fixing a refrigerant leak in an existing system): taxable.
• Adding a new zone to an existing system: likely qualifies as a new capital improvement, get a fresh ST-124 for that scope.

If a contractor bundles a new install and a repair on the same invoice without separating the line items, the entire amount becomes taxable. Always ask for split-line invoicing when two types of work occur on the same visit.

Homeowner Checklist: How to Claim the ST-124 Exemption

• Download the current Form ST-124 from tax.ny.gov (use only the current revision, outdated versions can be rejected).
• Fill in your name, property address, and a description of the work (e.g., “ductless mini split installation, outdoor condenser, 2 indoor heads, refrigerant line sets permanently affixed through exterior wall”).
• Check the box confirming you are the property owner (or tenant with owner authorization, verify with your contractor which applies).
• Sign and date the form before or at the time work begins, and no later than 90 days after completion.
• Give the original to your contractor; keep a copy for your records for at least three years.
• Verify your invoice shows no sales tax line for the installation service. If sales tax was charged in error, ask the contractor for a credit or refund; they can file for a refund with the NY Department of Taxation and Finance.

Common Mistakes to Avoid

• Signing as a tenant when you don’t own the unit: a tenant signature invalidates the certificate; the contractor must then collect tax.
• Using ST-124 to buy equipment tax-free: the form only exempts the installation service, not the purchase of the mini split units themselves.
• Providing the form after 90 days: the contractor is not required to accept a late certificate.
• Accepting a bundled invoice mixing install and repair: without split lines, the whole amount becomes taxable.
• Confusing TP-385 with ST-124: telling your contractor “HVAC is tax-exempt” based on the energy exemption is wrong and can lead to an underpayment issue.
• Skipping the form because the contractor “doesn’t charge tax”: without a signed ST-124 on file, the contractor has no legal protection in an audit and may pass back-taxes to you.

Frequently Asked Questions

Is a mini split installation always a capital improvement in New York?

Generally yes, if the system is permanently affixed, condenser bolted to the building, line sets routed through cored wall penetrations, indoor heads hardwired to a dedicated circuit. A portable or window AC that can be removed without damage does not qualify. When in doubt, describe the installation method in detail on the ST-124 form so the permanence is documented.

Does the ST-124 exemption cover the equipment (the mini split units themselves)?

No. Form ST-124 exempts the service of performing the capital improvement, the labor and the contract price for the installation. The contractor pays sales tax on the equipment at their supply house and absorbs it into their contract price. You cannot use ST-124 to purchase the outdoor unit or indoor heads tax-free.

What if my contractor already charged me sales tax on the installation?

If the job qualified as a capital improvement and you provide a valid signed ST-124, the contractor can issue a credit or refund for the tax collected. If they refuse, you or the contractor can file for a refund directly with the NY Department of Taxation and Finance. Keep your invoice and a copy of the signed ST-124 as supporting documentation.

Who signs the ST-124 for a co-op apartment in NYC?

The property owner signs, in a co-op, that is the co-op corporation, not the individual shareholder. For interior work contracted solely by the shareholder, practices vary; confirm with your managing agent before signing. An invalid signer creates an invalid certificate, and the contractor must collect tax on the full amount.

Are annual mini split maintenance visits also tax-exempt under ST-124?

No. Maintenance and repair services are taxable in New York. ST-124 applies only to the original capital-improvement installation (or a qualifying upgrade). Your annual tune-up invoice will include sales tax on both labor and parts, that is correct billing. Ask your contractor to invoice maintenance separately from any upgrade or new-install work to avoid a bundled taxable charge.