File non-resident imputed income tax (Modelo 210) on a Spanish property you don't rent out — based on cadastral value, due by 31 Dec of the following year, while not yet tax resident

The title describes Spain's quirkiest property tax: own a Spanish home while not (yet) tax resident and Hacienda imputes a notional income on it — even if it sits empty — filed on Modelo 210 by the title's deadline. It stops applying once you're tax resident; until then it's an annual ritual many owners genuinely never hear about until the letter arrives.