Schockemohle’s frozen contract is perhaps one of the most restrictive in the market. It’s a relatively “new” thing (4 years old now? maybe? …time is a lie…) but clearly designed to restrict people who were splitting doses and getting multiple pregnancies from them. Under the terms of their new contract, you must either send the used straws back (or clearly photograph the straws post-use).
They also state that they will re-invoice a separate stud fee for each embryo, when ICSI is being done (which may only be done with prior agreement).
You’ll see people who look for Schockemohle stallions’ frozen that pre-date these contracts because there’s quite a few restrictions/limitations. SES has the PS contract hosted if you are curious.
eta: to my knowledge, I don’t think anyone else’s contracts are quite this restrictive, but I haven’t really paid attention to frozen in the last few years so I’m not entirely certain if some of the big studs didn’t follow in PS’s footsteps - it would not surprise me if some had.