Its been a while (30+ yrs) since I haven't been self employed, but I thought that pre-tax benefit payments were a 'no-brainer'.
I used to work in the temporary help industry, & we were always looking for the clients' angles in the benefits packages.
I thought it was a 'given' that most deductions were pre-tax unless otherwise regulated.
When I had employees, my accountant set up their benefits as pre-tax deductions.