Yes he does need to file an sa100. Rules are different for income tax and Corp tax.
There is an automatic penalty for non compliance with daily penalties applied if the return is not filed within 3 months of the due date. If hmrc haven't issued a notice to file then you will have 3 months from the date of registration to file the return.
You are supposed to register by 5th October following the end of the tax year and any paper return has to be submitted by 31st October or else it's an e return by 31st January.
Hmrc no longer allow penalties to be waived in the case of nil returns so make sure you file it. Google SA1, complete and send to hmrc.
Edit: if the company does start to trade you will need to complete a CT41G informing hmrc that the company is no longer dormant. Failure to comply results in severe penalties.
Accounts need to be filed with companies house whether the company has traded or not