Is there an extension available for the Modelo 210 deadline?

No — there is no automatic extension available for the Modelo 210 deadline. Unlike some other tax systems — such as the UK's Self Assessment, which allows extensions in certain circumstances — Spanish tax law provides no standard mechanism for extending the non-resident filing deadline. The deadlines (31 December of the following year (tax year 2025; from tax year 2026, changed deadlines apply per Orden HAC/623/2026) for imputed income, 1–20 January for rental income) are fixed by statute and not negotiable. A theoretical exception exists for force majeure (fuerza mayor) — natural disasters, serious illness, or demonstrably unavoidable circumstances that make timely filing impossible. In practice, this exception is very rarely invoked for IRNR declarations and even more rarely accepted. Anyone seeking to rely on it must submit a formal application to the AEAT with supporting documentation. The practical approach to an impending deadline is therefore straightforward: file immediately, even if the documentation is incomplete. A surcharge of 1% for one month's delay is substantially cheaper than any alternative. If, for example, a British owner realises on 28 December that the imputed income deadline falls on 31 December and they lack the cadastral details: it is better to file with the available information and submit a correction afterwards than to let the deadline pass. For rental income, the filing window (1–20 January) is particularly tight. An owner who realises on 21 January that they have missed the deadline should file that same day — the surcharge for one month's delay is a mere 1% of the tax liability. A Gestor or Asesor Fiscal can prepare the filing at short notice provided the essential data is available: NIE, cadastral reference, ownership share, usage periods, and rental income if applicable.