Funny you should say that, we have a Firearm Certificate system here whereby you need a certificate for each gun, not one certificate for the owner.
You have to give details of the gun on your application which takes about 3 months to go through, so you go find a gun, pay a deposit, put the serial number, make etc on the application and wait, the strange thing is I was not asked anywhere on the form if the gun was silenced only if it had been modified and seeing as the moderator was factory fitted it was not modified. Yet in the rifle and handgun section on the form they DO ask, I guess the system here is not geared to deal with moderated shotguns as I get disbelieving looks when I tell people I have a silenced shotgun, very rare here and maybe a loophole in the law, although when you apply you must send a covering letter with the application and I said in the letter that the reason for this type of gun was it's quietness when shooting say rats.......still they never raised a query.