Every year, millions of taxpayers file their income tax returns with the Spanish Tax Agency, and many of them make avoidable mistakes. These errors can lead to inconvenient notifications, delays in refunds and even heavy penalties.
That is why today we will explain how to identify and avoid common income tax errors, thus ensuring a correct income tax return.
Main errors in the Income Tax Return
Every year, small oversights cause tax storms. Knowing the main mistakes in your tax return is your best defence. Get ready to avoid them!
Not checking your draft tax return properly
The first and most common mistake is to rely entirely on the draft tax return provided by the Tax Agency. Although the pre-filled information makes the process easier, it is your responsibility to check that it is correct. Be sure to carefully review each piece of information, especially deductions, income and withholdings.
Omitting additional income
Many people forget to include additional income such as rental income, temporary jobs or investments. This oversight can lead to penalties on your tax return, as the Tax Agency has access to a large amount of tax information.
Errors in applying tax deductions
Tax deductions can significantly reduce your tax bill. However, applying them incorrectly or not taking advantage of them is another common mistake. Knowing what deductions are available and applying them correctly will prevent future problems and allow you to optimise your refund.
Filing your income tax return after the deadline
Forgetting the income tax return deadline may seem like a minor oversight, but it results in automatic surcharges and even penalties. Mark the deadlines clearly and file your return well in advance so that you have time to correct any errors or clarify any doubts.
Failure to file a supplementary return when required
If you discover errors after filing your return, failure to file a supplementary return may result in higher penalties. It is important to identify and correct these errors as soon as possible to minimise potential fines.
Practical tips to avoid mistakes on your income tax return
Don’t let your numbers become a maze or a mistake. Follow these practical tips and ensure a smooth ride on the income tax road:
Keep your documents organised
A good practice is to keep all your documents organised throughout the year. Invoices, contracts, withholding certificates and bank information should be easily accessible and well organised. This will help you quickly verify the information on your draft tax return.
Always consult with experts
When questions arise, especially with complex issues such as investments or specific deductions, turning to tax professionals can make the difference between a correct return and one full of errors.
Use simulators before the official filing date
The Tax Agency’s simulators or online tools are very useful for detecting possible errors before filing your final income tax return. These systems allow you to check different scenarios and choose the best tax option.

Consequences of making mistakes on your tax return
Income tax errors are not just an administrative hassle; the financial consequences can be significant. From small surcharges to severe penalties depending on the severity of the error, every mistake has a potentially high cost.
It is essential to understand that the Tax Agency has up to four years to review your returns, which means that a seemingly insignificant error could cause you problems even years later.
What should you do if you have already made a mistake?
If you notice an error after submitting your tax return, act quickly:
- Clearly identify the error.
- a supplementary return if necessary.
- Consult an expert to properly handle the correction.
Proactivity is essential, as quickly correcting errors can prevent further complications and minimise penalties.
Why rely on professional tax advice?
Hiring the professional services of an advisor is key to avoiding all these problems. Specialised professionals are fully familiar with current tax legislation, are constantly up to date and have experience in optimising income tax returns.
In addition, delegating the filing of your tax return to an advisor allows you to save time and gain peace of mind, knowing that everything has been thoroughly reviewed by experts.

Avoid mistakes and optimise your tax return with Orihuela Costa Advice.
Do you want to ensure your tax return is correct, avoid headaches and make the most of the tax deductions available? At Asesoría Orihuela Costa we offer comprehensive solutions that include:
- Comprehensive advice for individuals.
- Advice for companies, helping you to comply with all your tax obligations.
- Specialised advice for SMEs, adapting to your specific needs.
- Personalised services for the self-employed, facilitating efficient tax management.
- Complete administrative services to simplify all your paperwork.
Don’t wait to receive unexpected penalties. Trust experienced professionals, avoid costly mistakes and optimise your tax results.
Request the services of Asesoría Orihuela Costa now and enjoy an accurate, error-free and profitable tax return.