How do I calculate the self-use and rental portions?

The split is generally made by calendar days. Rental days are the days on which an effective rental agreement existed and rental income was actually received. Self-use and vacancy days are all remaining days of ownership in the calendar year. Example: an owner holds a property for the full year (365 days) and lets it for 90 days in summer. Rental portion: 90 days. Self-use portion: 275 days. For the 90 rental days, actual rental receipts are taxed — as a separate Modelo 210 declaration with a deadline of 1–20 January of the following year (tax year 2025; from tax year 2026, changed deadlines apply per Orden HAC/623/2026). For the 275 self-use days, imputed income is calculated pro rata: cadastral value × imputation rate × 275/365 × tax rate × ownership share — as a separate Modelo 210 declaration with a deadline of 31 December of the following year. With co-ownership, a further split by ownership share is made: each co-owner declares their share of the rental income and their share of the imputed income. Two declarations per owner.