There is a specifically Qualified reimbursement arrangement that would be tax free:

https://www.healthcare.gov/small-businesses/learn-more/qsehra/

"To qualify for a QSEHRA, a small employer generally must:

• Have fewer than 50 full-time employees
• Provide the arrangement on the same terms to all full-time employees (reimbursement amounts may only vary based on age and the number of individuals covered)
• Not offer a group health plan, like SHOP coverage or a flexible spending account (FSA)"