Does anyone know if denting the silencer box on the rear tail pipe damages the exhaust?

So long as it’s not a big dent (i.e. impinging on internal pipework) it will almost undoubtedly make sod all difference that you’ll notice. Pic?

Generally backboxes are mostly volume filled with either baffles or fibreglass wool. Obviously if you dent the volume you reduce it, which can alter the tuned frequency and make it slightly noisier but I suspect you’d not notice. It could loosen a baffle which may rattle, but ultimately it wont matter to you.

No idea why its in the bike section though 🙂

Standard backbox contents:

Cheers for the reply, the reason I ask is because I just got brand new exhaust fitted and it has a dent in the back box! Not sure if its worth complaining over. Sorry, didn’t mean to put it in the bike section.

Not unless it is right near a seam and has caused a split, or unless its quite large and obviously likely to cause a restriction in flow, IMO. Judgement call, only you know how much you care about the exhaust. If it were my stainless box with a lifetime guarantee I’d moan, if it were my £25 backbox for my pug I’d ignore it.