I read the actual legislation before teaching a class on AZ Updates and I recall it said something about if you elected to use the SBI you had to put all your SBI on it.  I was reading it to kind of see whether someone who had perhaps half Schedule C, and then had Schedule E (maybe rental or S-corp) - and interpreted it that they had to put all of it on SBI or none.  So, no I don't think if someone has mostly self-employment that they can put only up to the 4.17% bracket on the 140, and then the rest on the SBI.