Spain’s annual income tax campaign is about to get underway, with millions of taxpayers anticipating to file their returns, many will make the same avoidable mistakes as every year.

The 2026 Declaración de la Renta campaign, covering income earned in 2025, opens for online filing on April 8 and runs until June 30, according to the Agencia Tributaria.

From failing to declare foreign income to relying too heavily on the draft return, small errors can delay refunds or trigger penalties. The risks are especially high for expats and freelancers, whose tax situations tend to be more complex.

Here are the most common mistakes—and how to avoid them before submitting your return.

Not declaring worldwide income in your Spain tax return

One of the most serious errors is failing to declare income earned outside Spain. If you are a tax resident, you are required to report all global income, including salaries, pensions, dividends, and rental income from abroad.

Many expats assume that income taxed in another country does not need to be declared in Spain. This is incorrect. Spain’s double taxation treaties may prevent you from being taxed twice, but they do not eliminate the obligation to declare.

How to avoid it: Report all income sources and apply relevant tax credits where applicable.

Misunderstanding tax residency rules in Spain (183-day rule explained)

Residency status is one of the most misunderstood aspects of Spain’s tax system. If you spend more than 183 days in Spain during a calendar year, you are generally considered a tax resident.

There is no split-year system, which often surprises newcomers and remote workers.

How to avoid it: Track your time in Spain carefully and confirm your residency status before filing.

Missing Spain’s tax filing deadlines and facing penalties

Failing to file on time is a common and avoidable mistake. Spain’s tax campaign typically runs from April to June, with penalties applied for late submissions.

Even minor delays can trigger surcharges that increase the longer you wait.

How to avoid it: Prepare your documents early and submit well before the deadline.

Errors in the draft tax return (borrador) from the Spanish tax agency

The draft tax return provided by the Agencia Tributaria, known as the borrador, is a helpful starting point, but it is not always accurate.

It may omit foreign income, property details, or recent financial changes.

How to avoid it: Review the draft carefully and cross-check it with your own records before confirming. Use an online calculator to estimate your overall tax position and get an idea of what you may owe.

Failing to report foreign assets with Modelo 720

Expats and international investors often overlook Modelo 720, which requires residents to declare foreign assets exceeding 50,000€.

Although rules and penalties have evolved in recent years, the obligation to report remains.

How to avoid it: Disclose all qualifying overseas accounts, investments, and real estate holdings.

Incorrectly declaring rental income and second home tax (imputed income)

Property-related mistakes are among the most frequent issues flagged by tax authorities.

Common errors include:

• Not declaring rental income

• Forgetting “imputed income” on second homes

• Claiming unsupported expenses

Even properties that are not rented out may still generate taxable income based on their cadastral value.

How to avoid it: Understand how property income is taxed and keep proper documentation for deductions.

Overlooking tax deductions and regional benefits in Spain

Spain offers a range of deductions at both the national and regional level, but many taxpayers fail to claim them correctly, or miss them entirely.

These may include deductions for:

• Pension contributions

• Family status

• Rental expenses

• Regional tax credits

How to avoid it: Research available deductions in your autonomous community or consult a tax advisor.

Filing the wrong tax form (Modelo 100 vs Modelo 210)

Using the wrong form is a frequent mistake, particularly among expats.

• Modelo 100 is used by tax residents

• Modelo 210 is for non-residents

Filing incorrectly can lead to delays or penalties.

How to avoid it: Confirm your residency status and ensure you are submitting the correct form.

Poor record-keeping that can trigger tax audits in Spain

Inadequate documentation can quickly become a problem if your return is reviewed.

Missing invoices, incomplete records, or lack of proof for deductions may result in adjustments or fines.

How to avoid it: Keep all relevant financial records for at least four years, as required by Spanish law.

Misclassifying income types (savings vs general tax base in Spain)

Spain separates income into different tax bases, such as general income and savings income.

Misclassifying items like capital gains, dividends, or interest income can lead to incorrect tax calculations. Note, cryptocurrency assets are also subject to tax.

How to avoid it: Ensure each type of income is reported in the correct category to avoid discrepancies.

How to avoid costly errors when filing your Spain tax return

Avoiding mistakes comes down to preparation and attention to detail. The most common issues such as undeclared income, incorrect residency status, and missed deductions, are preventable with proper planning.

For expats, the complexity increases due to cross-border income, foreign assets, and differing tax systems.

Taking the time to review your return thoroughly, even if you’re working with a professional, can significantly reduce your risk.

What to do before submitting your declaración de la renta in Spain

Before filing your tax return, make sure you:

• Have declared all worldwide income

• Verified your residency status

• Reviewed the borrador carefully

• Checked all deductions and credits

• Confirmed you are using the correct tax form

Filing an accurate return helps avoid penalties and ensures any refund is processed without delays. Taxpayers with more complex situations may want to consult a professional to avoid errors or unexpected liabilities.

FREQUENTLY ASKED QUESTIONS

Who needs to file a tax return in Spain in 2026?

It depends on your income level and employment status, but most residents above certain thresholds must file.

What happens if I file my Spain tax return late?

Late filings can result in penalties and surcharges that increase over time.

Do I need to declare foreign income in Spain?

Yes. Tax residents must declare worldwide income, even if it was taxed abroad.

Is the Spanish tax draft return accurate?

Not always. It may contain missing or outdated information and should be reviewed carefully.