Iowa Construction Sales Tax Exemption Certificate: Uses, Suppliers, and Refunds

An Iowa construction sales tax exemption certificate lets a contractor buy building materials for a qualifying project without paying the state’s 6% sales tax, but the certificate has to come from the project owner, not the contractor. Under Iowa Code section 423.3(80), the owner (a “designated exempt entity” such as a city, county, school district, or state agency) registers the construction contract with the Iowa Department of Revenue through an online application. The Department then generates a project-specific exemption certificate and a purchasing agent authorization letter that the entity passes to each contractor and subcontractor, who in turn present them to material suppliers at the point of sale.¹

Who Issues the Certificate

Only the exempt entity can start the process. A contractor cannot generate the certificate independently, and there is no blank version to download. The entity logs into the Department of Revenue’s online application, registers the construction contract, identifies every contractor and subcontractor working on it, and then prints the exemption certificates and purchasing agent authorization letters directly from the system.¹

This matters because working for a government body does not, by itself, make a contractor tax-exempt. Iowa Administrative Code rule 701-212.12 states that contractors on federal, state, county, or municipal jobs remain subject to sales and use tax on materials they purchase unless the exempt entity has gone through the formal registration process.² The exemption belongs to the entity. Without the certificate in hand, you pay full tax.

What the Certificate Covers

The exemption reaches building materials, supplies, equipment, and services that meet two conditions: the items must be completely consumed in performing the contract, and the finished property must become public property or property of the designated exempt entity.³ Lumber that becomes a wall qualifies. The saw that cut it does not.

The Department of Revenue identifies several categories of purchases that stay taxable even on an exempt-entity job because they never become part of the completed real property:

Equipment and vehicles such as cranes, compressors, grading and excavating vehicles, electric generators, and pile drivers
Consumable supplies including fuel, dynamite, and replacement parts for equipment
Temporary-use items like scaffolds, forms, barricades, stakes, and warning lights
Hand tools, lathes, and drill presses
Lodging and utilities for the crew

Machinery or equipment that stays as personal property rather than becoming part of real property can be bought tax-free for resale to the exempt entity, but the contractor has to itemize and transfer that property to the entity separately.¹ Contractors who also hold an Iowa sales or use tax permit and sell building materials at retail may withdraw materials from their own inventory tax-free for an exempt-entity project as long as they hold a valid certificate for that contract. The same rule applies to manufacturers fabricating materials for the job.³

How to Use It With Suppliers

Give the supplier both documents (the exemption certificate and the purchasing agent authorization letter) before or at the time of purchase. The supplier keeps them on file as the justification for not collecting the 6% state sales tax or any local option tax, which is typically 1% in most Iowa jurisdictions.⁴ Without them, the supplier has no audit protection and should charge the full tax.

Each certificate ties to one specific construction contract. If you are working on three exempt-entity projects at once, you need three certificates. There is no blanket certificate that covers all of a contractor’s exempt-entity work; every one has to be generated through the Department’s online application for a particular registered contract.¹

If There Is No Certificate: The Refund Route

When the exempt entity does not register the contract in advance, the exemption still exists, but it moves to the back end of the project. The contractor pays Iowa sales tax on all building materials and builds that cost into the bid. After the work is done, the contractor fills out an Iowa Contractor’s Statement (Form 35-002) documenting the sales and use tax paid on materials that went into the real property. The exempt entity submits that statement along with a Construction Contract Claim for Refund (Form 35-003) to the Department of Revenue to recover the tax.¹

For some owners, the refund route is the only option. Businesses located in economic development areas and rural water districts organized under Iowa Code Chapter 504A do not qualify as designated exempt entities and cannot use the upfront certificate process at all.¹

Which Projects Actually Qualify

Iowa Code section 423.3(80) defines a designated exempt entity by cross-reference to the entities listed in section 423.4(1) and 423.4(6).³ In practice, the owners whose projects qualify for the upfront certificate include:

Counties, cities, school districts, regional transit systems, and their boards, commissions, and agencies
The Board of Regents and its universities, the Department of Health and Human Services, and the Department of Transportation
The governing body of any federally recognized Indian tribe
Government divisions, boards, or instrumentalities whose earnings do not benefit private investors or stockholders

If the owner on your contract is a private business, a for-profit developer, or a nonprofit that is not on this list, the construction exemption does not apply, even if the project will be leased to a government body later.

Don’t Confuse It With Form 31-014

Three Iowa forms get mixed up constantly in construction tax conversations, and using the wrong one at the register does not create a valid exemption.

The exemption certificate and purchasing agent authorization letter generated through the Department of Revenue’s online application are what you present to suppliers on an exempt-entity construction job. There is no blank version.¹
Iowa Contractor’s Statement (Form 35-002) is only for the refund process after the contractor has already paid tax on materials.¹
Iowa Sales/Use/Excise Tax Exemption Certificate (Form 31-014) is a general-purpose exemption certificate for various sales tax exemptions. It is not the construction contract exemption and should not be handed to a supplier in place of the online-generated certificate.⁵

A contractor who gives a supplier Form 31-014 when the transaction calls for the contract-specific online certificate has not properly claimed the construction exemption, and both parties carry the audit exposure.

Recordkeeping and What Misuse Costs

Suppliers who accept the exemption certificate should keep it on file for at least three years, according to the Department of Revenue’s guidance.¹ Contractors and exempt entities should hold their own copies for the same period. If no one can produce the certificate during an audit, the Department can assess the unpaid tax plus interest and penalties.

The penalty schedule for sales and use tax underpayments includes:

5% for late filing when a return is not filed by the due date and less than 90% of the correct tax was paid
5% for late payment when less than 90% of the correct tax is paid on time (this can stack with the late-filing penalty)
5% audit penalty when the Department discovers an underpayment during an examination
75% fraud penalty for fraudulent claims or willful failure to file, which cannot be waived
$1,000 per unfiled return when a taxpayer fails to file within 90 days of a Department demand letter

Iowa also charges interest at 10% per year on unpaid balances as of 2026.⁶ A contractor who improperly bought $200,000 in materials tax-free faces back tax, a 5% audit penalty, and interest that keeps running until payment. Deliberate misuse of a certificate moves into the 75% fraud range, which cannot be negotiated down.

The exemption is project-specific. If you use certificate-purchased materials on a taxable job, or divert them to another contract that was never registered, you owe the tax on those materials and the exemption does not protect you.

1
Iowa Department of Revenue. Construction Contracts with Designated Exempt Entities
2
Iowa Legislature. Iowa Administrative Code 701-212.12 – Sales to Federal, State, Municipal, and Tribal Governments and Instrumentalities
3
Justia Law. Iowa Code Section 423.3 – Exemptions
4
Iowa Department of Revenue. Sales and Use Tax Guide
5
Iowa Department of Revenue. Iowa Sales/Use/Excise Tax Exemption Certificate
6
Iowa Department of Revenue. Penalties and Interest Rates