Ohio Commercial Activity Tax Update: Platform Transition and Proposed Rules for Businesses

As we move through the final months of 2026, Arnold Gruber, Ltd., Attorneys at Law continues to monitor tax developments that affect businesses operating in Ohio. Two near-term changes involving the Commercial Activity Tax (CAT) deserve attention from companies that have Ohio taxable gross receipts.

Transition to OH|TAX eServices

The Ohio Department of Taxation is moving CAT filing and payment from the Ohio Business Gateway to the OH|TAX eServices platform. The final CAT return that can be filed through the Ohio Business Gateway is the third-quarter 2026 return, due November 10, 2026. Beginning November 23, 2026, CAT filings will no longer be available on the Gateway. All CAT accounts will migrate to OH|TAX on December 7, 2026.

The new platform is designed to simplify compliance. Features include instant registration for new or reopening accounts, the ability to complete credit schedules directly on the electronic return, Excel uploads for updating corporate structures, and faster return processing. Taxpayers are encouraged to establish an Ohio ID (OHID) and enable multi-factor authentication before the transition. Existing Gateway access is expected to transfer automatically, but early preparation can reduce the risk of filing delays.

Proposed Rule Amendments

Separately, the Department has proposed amendments to three CAT administrative rules and is accepting public comments through October 27, 2026. Proposed Rule 5703-29-09 would clarify the process for requesting and applying overpayments of estimated CAT payments and remove outdated language. Proposed Rule 5703-29-22 would eliminate the reference to the refundable net operating loss credit to conform with recent legislation (H.B. 96). Proposed Rule 5703-29-02, addressing common owners and joint ventures, is being refiled without substantive change. No effective date has been announced.

These updates affect registration, estimated payments, refunds, and ongoing compliance for businesses above the $6 million exclusion threshold, as well as companies managing multi-entity structures. Now is a practical time to confirm account status, review estimated payment procedures, and ensure the appropriate personnel have OHID access before the December migration.

At Arnold Gruber, Ltd., our attorneys assist businesses with Ohio tax compliance, multi-state planning, and related corporate matters. We can help evaluate the impact of the platform transition, review estimated payments and credits, and prepare for the new filing environment. Please contact us at (330) 563-4149 to discuss how these changes may affect your operations.