The New Jersey ST-13 Contractor’s Exempt Purchase Certificate

In New Jersey, the ST-13 Contractor’s Exempt Purchase Certificate lets a contractor buy construction materials, supplies, and certain services without paying the state’s 6.625% sales tax when the work improves real property owned or leased by a qualifying exempt entity.¹ You fill the form out, hand it to your supplier, and the supplier drops the sales tax off the invoice.²

Whose Projects Qualify

The ST-13 works for only three kinds of property owners, and each brings its own paperwork you need in hand before you buy anything.³

The first is a government entity: any agency, political subdivision, authority, or public corporation of the United States or the State of New Jersey. Municipal departments, public school districts, county governments, and federal facilities located in New Jersey all count. Agencies of other states do not. Work for a Pennsylvania agency, even on a site in New Jersey, is not covered.²

The second is an exempt organization that already holds a valid New Jersey ST-5 Exempt Organization Certificate. Ask for a copy of that ST-5 before you start buying. Without it, you have no basis to claim the exemption.⁴

The third is a qualified housing sponsor. New Jersey recognizes two kinds: an entity certified by the New Jersey Housing and Mortgage Finance Agency that obtained financing under N.J.S.A. 55:14K-1 supplementing government subsidies, and any entity engaged in affordable housing projects where every unit is restricted to moderate-, low-, or very-low-income occupants. A housing sponsor must give you a Sales and Use Tax Housing Sponsor Letter of Exemption before you use the ST-13 on the project.²

What You Can Buy Tax-Free, and What You Can’t

The exemption covers construction materials, construction supplies, and certain qualifying services, but only when they are used exclusively and entirely consumed in erecting, building on, improving, altering, or repairing the exempt entity’s real property.³ Lumber framed into a wall, drywall on the studs, plumbing fixtures installed in a bathroom, and consumables like caulk, sandpaper, and paint used up on site all qualify.

Equipment does not. Bulldozers, jackhammers, hand tools, power tools, computers, and rented machinery like cranes or scaffolding stay taxable, no matter who owns the building. The rule of thumb: if the item leaves the job site in your truck at the end of the day, the ST-13 almost certainly doesn’t cover it.³

Exclusive use matters too. Buy a pallet of lumber, use half on the exempt project and half on a private client’s deck, and the whole purchase fails the test. Split your orders so each one is dedicated to a single project.

Filling Out the Form

The current ST-13 is available as a fillable PDF from the New Jersey Division of Taxation at nj.gov/treasury/taxation. Every field has to be completed. An incomplete certificate is treated as no certificate, and the seller will charge you the full 6.625%.²

You’ll need:

Your full legal business name and address as they appear on your tax filings.
Your New Jersey taxpayer identification number, issued when you registered with the NJ Division of Revenue and Enterprise Services. Out-of-state contractors not registered in New Jersey can use their federal employer identification number or their home state’s registration number instead.⁵
The box checked for the exempt entity type: government entity, exempt organization, or qualified housing sponsor.
The name and address of the exempt entity whose property you’re improving.
The contract work site address. The property must be owned or leased by the exempt entity.
A description of the materials, supplies, or services specific enough that an auditor can connect the purchase to the project.
A signature from the contractor or an authorized employee. A paper or faxed certificate without a signature is invalid.⁵

Blanket or Single Purchase

At the top of the form there’s a checkbox for a blanket certificate. Checking it lets one ST-13 cover multiple purchases of the same general type of property or service from the same supplier, as long as no more than 12 months pass between transactions.² Each follow-up invoice or sales slip has to be clearly marked with your name, address, and taxpayer ID number.

Leave the box unchecked and the certificate covers only the single transaction described on it. You’ll need a new ST-13 for each purchase.

A blanket certificate only works while the qualifying facts stay the same: same project, same exempt entity, same type of materials. Start a new project for a different exempt client and you need a new certificate, even at the same supplier.

Delivering the Certificate to Your Supplier

Hand the completed ST-13 to the seller at the time of purchase, or within 90 days after the sale date. That 90-day window is a hard deadline. A seller who receives a fully completed certificate within that period is relieved of liability for the uncollected sales tax even if the exemption claim later turns out to be improper; in that case the contractor, not the seller, owes the tax.²

Delivery method doesn’t matter. Paper at the register, a fax, or a PDF emailed to the seller’s accounting department all work, as long as the form is complete and legible.

Sellers can refuse a certificate that looks incomplete or that clearly doesn’t match the transaction. If you get pushback, check every field. A missing taxpayer ID or a blank work site address is usually the reason.

Keeping Records

Sellers have to keep every ST-13 on file for at least four years from the date of the last sale covered by that certificate.⁶ For a blanket certificate covering purchases across many months, the clock runs from the final transaction, not the first. Digital copies are fine as long as they’re legible and complete.

Keep your own copies too. The four-year rule explicitly targets sellers, but a contractor who can’t produce documentation during an audit faces the same practical problem: every unsupported purchase gets treated as a taxable sale, and you carry the burden of proving otherwise.⁶

What Happens If You Use the ST-13 Wrong

Using an ST-13 for purchases that don’t qualify, whether that’s materials for a private client’s project or equipment that won’t be incorporated into the exempt property, violates New Jersey tax law. When the Division of Taxation determines a contractor claimed the exemption improperly, the contractor owes the full sales tax that should have been collected plus a 5% penalty on the unpaid amount.⁷ Interest accrues on top of that at three percentage points above the prime rate, compounded annually.

A seller who accepted the certificate in good faith is generally protected. A seller who knew or should have known the certificate was bogus can lose that protection and face its own assessment.²

Mistakes That Show Up in Audits

The same errors surface again and again. Leaving the work site address blank is the most common; without it, the seller can’t verify that the property belongs to an exempt entity. Forgetting to collect or reference the exempt entity’s ST-5 or Housing Sponsor Letter of Exemption is another one that unravels the whole claim months later.

Contractors also get caught buying tools, rented equipment, or office supplies on an ST-13 on the theory that anything used “for” the exempt project qualifies. It doesn’t. The exemption only covers items physically incorporated into the property or consumed on site during construction. Put tools and rentals on separate invoices with sales tax applied, and save the ST-13 for the materials that actually end up in the building.

Watch the entity type as well. Urban Enterprise Zone projects use a different form, the UZ-4, not the ST-13.⁸ Handing the wrong certificate to a supplier creates a problem that only surfaces at audit, when the original transaction is long past reconstructing.

1
NJ Division of Taxation. Sales and Use Tax
2
New Jersey Division of Taxation. ST-13 Contractor’s Exempt Purchase Certificate
3
NJ Division of Taxation. Sales and Use Tax Exemption for Contractor Purchases
4
New Jersey Division of Taxation. Form REG-1E Application for ST-5 Exempt Organization Certificate
5
New Jersey Division of Taxation. Contractor’s Exempt Purchase Certificate
6
State of New Jersey Department of the Treasury. ST-13 Contractor’s Exempt Purchase Certificate
7
Legal Information Institute. New Jersey Administrative Code 18-2-2.4 – Failure to Pay on Time
8
NJ Division of Taxation. Division of Taxation – Urban Enterprise Zone Tax Certificates