Complex sentence: It was one of the many measures against Caelibes (celibites), unless they married within 100 days, not only did they have to pay the tax, but also couldn't have a hereditas or a legacy (legatum) Ulp.
Split into simpler sentences: It was one of the many measures against Caelibes (celibites), unless they married within 100 days. Not only did they have to pay the tax, but also they could not have a hereditas or a legacy (legatum) Ulp.