We have a Mac here which has been inherited from another user. How do you remove App Store software from a Mac, when you don't have access to the account that installed it.

We can't update the app, because the user account is unknown and we can't bin the app, because it requests the user ID of the account that installed it from the App Store...

Have you tried an app cleaner like Appcleaner?

Just wipe the thing and start again.

I've already suggested that, not an option.

Just create a new administrator account in System Preferences > Users & Groups (or > Accounts for 10.7 or earlier) log-in to that and then bin the old one in the same place (clicking the little [-] button) - then just trash the old software from the Applications folder, most software from the App Store doesn't install lots of files into the system, maybe the odd folder in the top level Library/Application Support.

If you don't have the OS X administrator password that the previous owner set (not the Apple ID) then you can reset it by booting from the recovery partition (or original system disc if it's an older Mac Pro).

He says that they can’t bin apps because it wants the credentials of the previous owner to do so. You may be able to do this from the recovery partition, or by booting it up in target disk mode and doing to from there.

The other alternative is to try using the command line in Terminal to remove the file - I’m afraid I don’t know what the commands would be for that, other that you’ll need to use sudo

It shouldn't ask for an Apple ID (iTunes/App Store account) in order to bin the software - it's probably asking for an administrator username and password which, if you don't know it, can be reset by booting from a system install DVD or the Recovery Partition.

Alternatively, boot from another volume with OS X installed (or boot into Firewire Target Mode attached to another Mac) and delete the software from the 'Applications' folder of the Mac's internal hard drive. Make sure you delete it from the correct drive though.