Posted: Fri Jul 8, 2022 9:26pm
Yes, even though it is a long process they can end up starting proceedings behind your back.
If the tax office is unable to notify you, they are entitled to make the notification public on the BOE (Boletín Oficial del Estado / official state gazette). This being public, legally has the same effect as if they have managed to deliver the notification directly to you.
This is one of the reasons why, for non Residents, it might be advisable to have a fiscal representative in Spain (solicitor, accountant, etc.). This way official notifications can be delivered to your representative and they can react and deal with it in a timely manner, as lots of tax porcedures are bound to very short time period to react.