It would appear to be the tax office (same as HMRC), so no connection with local taxes, car etc.
It is more likely to do with tax returns, maybe not being made, taxes owed etc.
I understand that many people are being contacted about not making tax returns either as non-residents, property owners, or residents who have not made an annual tax return (which is required by practically everyone, including those who are, or believe, their income is below the tax relief level. ‘negative return’ are usually still required).
I would suggest you contact Hacienda, or get someone to do so for you, Spanish speaking friend, gestor, etc. using your NIE. That should lead to your records and bring-up any outstanding matter. Do not just leave it.
This message was last edited by johnzx on 11/06/2014.