Second hand RSJ steel beams

Hi all,
I'm after a bit of advice regarding steel beams and building control. I'm building a garage extension and have consulted a structural engineer who has provided beam calculations etc. I've put in the building notice to the council and have started shopping around for steel beams. My question is, is it okay to buy secondhand/not used steel beams or will the building control inspector want to see some form of certificate regarding the steels?

Thanks in advance,
BASH0001