He says right on top that thats negotiable _upfront_. I usually have net 15 and am pretty strict on that. That means, I will call on that day and ask for the invoice to be paid. I also make it clear to clients that prolonged non-payment outside of terms will lead to a raise on the negotiation. I also make clear that if they cannot pay for whatever reason, they can just call and talk about things. The reason why the default number is low is pretty easy: clients will only go up from there.
I personally find the punishment extremely hard. 10% per week is definitely unreasonable. It would basically put that person on my "don't recommend that colleague"-list.
About companies not paying late fees: unless the contract is really beefy to start with, its also a quick way to ensure that good freelancers won't work with you again. Word goes around. I've seen more that one seemingly "big" company struggle with not having any business partners to turn to any more.
I personally find the punishment extremely hard. 10% per week is definitely unreasonable. It would basically put that person on my "don't recommend that colleague"-list.
About companies not paying late fees: unless the contract is really beefy to start with, its also a quick way to ensure that good freelancers won't work with you again. Word goes around. I've seen more that one seemingly "big" company struggle with not having any business partners to turn to any more.