If an individual purchased a plan on the marketplace, the ICHRA portion is pre-tax but the employee deduction would be post-tax.
This is why our system is focused on only showing OffExchange or OffMarket plans during the employee shopping. Most ICHRA vendors require the employee to pay the full premium so the pre-tax is not a consideration because the employee portion is already paid via post-tax personal funds. The benefitbay way is to use the ARC account and allow the employer to maintain the tax advantages of the full premium.
See screenshot below from healthcare.gov's article: