Form 100 is the self-assessment return for Personal Income Tax (IRPF — Impuesto sobre la Renta de las Personas Físicas) that fiscal residents in Spain file annually for the income, gains and losses generated during the tax year. The 2025 income tax campaign runs from 2 April to 30 June 2026, and covers all income, deductions and tax circumstances of the 2025 fiscal year. This guide explains how the form works, who must file it, what the exact deadlines are and the most common mistakes to avoid.
What Is Form 100 and When Must It Be Filed?
Form 100 is the annual IRPF return, the most significant tax for individual taxpayers resident in Spain. Through this form, the taxpayer self-assesses the tax due for the previous year, integrating all sources of income subject to IRPF: employment income, investment income and property income, income from economic activities, capital gains and losses, and income imputations.
The form is filed once a year, in the campaign that typically starts in April and ends on 30 June. There is no quarterly filing of Form 100; quarterly IRPF payments for self-employed persons are made using Form 130 (advance payments).
The applicable legislation is Ley 35/2006 on Personal Income Tax and its implementing regulation (Royal Decree 439/2007). The Ministry of Finance approves an annual Ministerial Order setting out the specific conditions for each campaign, the forms and the deadlines.
2025 Income Tax Campaign Calendar
2 April 2026: Opening of the online filing period. The AEAT enables access to the draft return and the 2025 fiscal year tax data on its electronic portal. Taxpayers can access using a digital certificate, electronic ID card or cl@ve.
First half of May 2026: Start of the Le Llamamos (We Will Call You) service. Taxpayers who do not have electronic means available or prefer assistance can request an appointment for an AEAT agent to call them and help them file by telephone.
First half of June 2026: Opening of AEAT offices for in-person filing by appointment. Appointments fill up quickly in the first few weeks; it is advisable to book early if you prefer this option.
25 June 2026: Last day to submit returns showing tax due if you wish to pay by bank direct debit. The AEAT will debit the account on 30 June.
30 June 2026: Final deadline for all types of result (tax due, refund or nil).
Who Must File
The obligation to file Form 100 applies to taxpayers who in the 2025 tax year received:
Employment income: obligation to file if it exceeds €22,000 gross per year from a single payer, or €15,000 if there are two or more payers and the second and subsequent ones paid more than €1,500 in total.
Investment income, property income and capital gains subject to withholding: if the total of these items exceeds €1,600 per year.
Imputed property income, Treasury Bill income and housing subsidies: if they exceed €1,000 in total.
Other income not subject to withholding: any such income exceeding €500 triggers a filing obligation.
Regardless of the above thresholds, the following are always required to file: self-employed persons with business income, those who made pension plan contributions with a right to a tax reduction, those who had to file Form 720 or Form 721, and those who traded in crypto assets generating capital gains or losses.
Even where there is no formal obligation, it may be worthwhile filing a return when the result is a refund (due to excess withholding) or when reliefs not applied in the draft would generate a refund entitlement.
Structure of Form 100: Main Sections
The IRPF return is structured as follows:
Identification and personal data. Name, tax ID number (NIF), fiscal domicile, family situation (marital status, number of children), matrimonial property regime and choice of individual or joint assessment.
Employment income (boxes 0001 onwards). Salaries, pensions, unemployment benefits, benefits in kind and any other employment income are recorded here. Withholding made by the payer appears on the withholding certificate, which must be kept as supporting documentation.
Property income. Rental income from property is declared and deductible expenses are offset (rates, service charges, insurance, depreciation, mortgage interest on the rented property). The reduction applicable to residential lettings (50%, 60%, 70% or 90% depending on the contract type and area) is calculated in this section.
Investment income. Dividends, bank deposit interest, savings insurance income and other financial income. Withholding made by the financial institution appears on their certificates.
Capital gains and losses. Disposals of property, shares, investment fund units, crypto assets and any other asset that generated a gain or loss are declared here. The calculation is the difference between the disposal value and the acquisition value (adjusted for expenses and commissions).
Business income. Self-employed persons under the direct assessment method (normal or simplified) or the objective method (módulos) declare their net income here. Advance payments made using Form 130 during the tax year are deducted from the resulting tax.
Taxable base and reduced taxable base. Calculated automatically by applying reductions to the general taxable base (pension plan contributions, compensatory payments, personal and family minimum allowances).
Gross tax liability. Calculated by applying the IRPF rate schedule to the general reduced taxable base and the savings rate schedule to the savings base.
Tax reliefs. State reliefs (maternity, energy efficiency, pre-2013 housing, charitable donations) and region-specific reliefs for each autonomous community are applied here.
Net tax liability. Calculated by subtracting withholding and advance payments made by payers from the gross tax. If positive, tax is due; if negative, there is a refund entitlement.
Filing Methods
Online filing (Renta WEB). The primary and recommended method. The AEAT makes the Renta WEB programme available on its electronic portal, which generates the draft with available data and allows the taxpayer to complete and submit the return online. It requires a recognised digital certificate, electronic ID card or cl@ve (the AEAT’s identification system with username and password).
Le Llamamos service (telephone). An AEAT agent calls the taxpayer at the requested date and time and assists them in completing and submitting the return by telephone. Aimed at returns of moderate complexity.
In-person assistance (AEAT offices). Filing by appointment at AEAT offices or at points set up by regional governments. Available from June 2026.
Through a tax adviser or administrative agent. The taxpayer can authorise a tax professional to access their tax data and file the return on their behalf using an authorisation or reference number.
Payment Options When Tax Is Due
When the return shows tax due, the taxpayer can choose:
Immediate payment. Pay the full amount when submitting the return, by bank account debit, card payment or at a collaborating financial institution (banks and savings banks).
Instalment payment. Pay 60% of the amount when submitting the return and the remaining 40% by 6 November 2026, with no surcharge or late payment interest. To take advantage of instalment payment, simply mark the relevant box on the form; the return must be submitted before 30 June 2026 (or before 25 June if the first payment is by direct debit).
Deferred payment. If the taxpayer cannot meet the amount, they can request a payment deferral from the AEAT under Article 65 of the General Tax Act. Approval is not automatic and late payment interest applies. This is not recommended as a routine planning tool.
The Renta WEB Draft: What It Includes and What It Does Not
The AEAT’s draft return contains data the administration holds in its records, sourced from:
- Withholding certificates from employers and pension payers.
- Financial institution information on interest, dividends and investment funds.
- Cadastral data on properties and their values.
- Information on property transfers reported by notaries.
- Social Security benefits (unemployment, incapacity, retirement).
However, the draft typically does not include:
- Region-specific tax reliefs.
- Overseas income not directly reported to the AEAT.
- Gains from share transactions through foreign brokers (Degiro, Interactive Brokers, etc.).
- Rental income without withholding.
- Crypto asset gains and losses.
- Nursery/childcare reliefs not reported by the educational centre.
- Loss offsetting from prior years that requires manual verification.
For this reason, confirming the draft without reviewing it is a common mistake that can result in both incorrect returns (overpaying tax) and subsequent AEAT adjustments (if income has been omitted).
Most Common Mistakes on Form 100
Not including overseas income. Fiscal residents in Spain are taxed on their worldwide income. Salaries from foreign employers, interest from overseas bank accounts, dividends from internationally listed shares and rental income from property abroad must all be included in the return even if the payer has not applied Spanish withholding.
Not declaring gains from foreign brokers. Share or ETF transactions through platforms such as Degiro, Interactive Brokers or Trading 212 are not reported by the broker to the AEAT and do not appear in the draft. The taxpayer must calculate and include them manually.
Incorrectly applying the residential letting reduction. Since the Housing Act 2023, the applicable reduction percentage for residential letting varies between 50% and 90% depending on the contract type and area. Automatically applying 60% without checking whether it is correct is a mistake the AEAT is now verifying through data cross-referencing.
Not offsetting capital losses from prior years. Losses from 2021, 2022, 2023 and 2024 pending offsetting can be applied against 2025 capital gains. The draft does not always incorporate these automatically.
Not applying regional tax reliefs. Regional tax reliefs do not appear in the draft and must be activated manually. Overlooking them can mean losing hundreds of euros of tax savings.
At BMC we carry out comprehensive reviews of IRPF draft returns, with particular attention to overseas income, crypto assets, regional tax reliefs and optimising joint versus individual assessment. For more information, visit our tax planning service page or request a consultation.
