A non-resident who only owns one property in Spain is allowed to file their own tax forms.
However, please note, the tax office does not send notifications of IBI tax to addresses outside Spain. It is therefore advisable for any person who has a property in Spain but doesn't live there all the time, to appoint a Fiscal Representative. A Fiscal Representative must be resident in Spain. The tax authorities will send all correspondence relating to your affairs in Spain directly to your Fiscal Representative. Appointing a Fiscal Representative will ensure that the Spanish tax authorities have a point of contact, so that unnecessary debts or fines can be avoided.
NIE Fiscal Number:
The NIE is your all-purpose identification and tax number in Spain. You need it for everything that involves an official process in Spain. For example, you will need an NIE number to buy a property, buy a car, get connected to the utilities and, most importantly as far as the Spanish state is concerned, pay your taxes. Without an NIE number, the Spanish tax authorities are unable to assess or process annual tax payments such as income tax (IRPF), and the annual wealth tax (Patrimonio), both of which are declared by resident and non-resident property owners.
Non Resident Taxes:
The non-resident property tax (Impuesto Sobre la Renta de no Residentes) is a tax on rental income for non-Spanish residents. If a property is rented, then income tax must be paid on the gross amount of rental income received at a rate of 24.75 percent (although since 2010, EU residents have been permitted to deduct allowable expenses).
Another tax applies to anyone who owns a property that is not their main home, and, if not rented out, a notional rental income is deemed to arise. The amount is derived from the cadastral value of the property. This amount can be found on the IBI council tax bill. The tax payable for a non-Spanish resident is 24.75 percent of a taxable amount calculated as 2 percent of the property's cadastral value (found on the IBI bill).
We recommend to all our clients that at some point they make a will in Spain to cover the bequeathing of their Spanish assets. In theory, a will made in their home country covers their world wide assets already.
However, if you have only made a foreign will then there are implications for your inheritors. For example, they will have to have an official translation and the Foreign Office and lawyers will have to be involved. Additional steps that make the procedure more complicated at a particularly difficult time.