Ninety day terms are very common in most B2B industries. Large companies quickly learn that their suppliers are dependant on them to stay in business and can be abused almost at will. So nominally "90 day" terms claiming you have 90 days to pay become "We definitely won't pay until 90 days after you bill us" and then "We typically pay in the working week after 90 days is due" and then "We only run routine bill payments on the third Wednesday of a month, so it can be up to 120 days I guess you got unlucky" and next thing you know the work you did in April is only paid for in October by a company that you know is already on the verge of bankruptcy but if you don't do that work they'll cut you off completely. It's crazy but that's how it is.
The EU says if in practice you don't pay on or before 90 days you owe interest at a calculated rate on the due amount. But most small suppliers are so in thrall to the huge company they supply that they won't even ask for that money.