Hi Giorgio,
If it is something that you need in order to be able to carry out your job and is used solely by the business, then generally, this would be an allowable expense. However, it likely wouldn’t be allowable if it has a dual purpose (business and personal use) or isn’t needed to carry out your job.
So, for a Bluetooth speaker, if its main purpose is so you can listen to music while you work, it’ll be a no.
Katie