Common Tax Mistakes: How to avoid them in your quarterly return
Patrick Gordinne Perez2025-03-04T05:14:32+00:00The quarterly declaration is one of the most important obligations for the self-employed and companies. However, many make common tax mistakes that can lead to sanctions, surcharges or problems with the Tax Agency.
If you want to avoid problems and optimise the financial management of your business, keep reading.
The 5 most common tax errors in the quarterly return and how to avoid them
Every quarter, thousands of entrepreneurs and freelancers face the filing of taxes, a process that can be complicated if not managed correctly.
Below, we explain the most frequent mistakes and how to avoid them so that your business runs smoothly:
1. Not submitting the return on time
One of the most serious and common mistakes is being late in filing taxes. The key dates for the quarterly declaration in Spain are:
- First quarter: until April 20.
- Second quarter: until July 20.
- Third quarter: until October 20.
- Fourth quarter: until January 30.
Extemporaneous surcharge
The surcharge for submitting a declaration after the deadline, and without prior financial request, is called the extemporaneous surcharge.
Delay in submission may result in surcharges ranging from 1% to 15% of the amount owed, in addition to possible penalties.
An effective solution is to establish automatic reminders or have a tax advisor in charge of the management and filing of taxes.
Learn with this article what are the surcharges for not paying a tax debt on time

What are enforcement surcharges?
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2. Errors in the VAT and personal income tax return

One of the most frequent problems is miscalculating the VAT incurred and passed on, which can lead to incorrect settlements. In the case of personal income tax, many self-employed people forget to include certain incomes or apply deductions incorrectly.
Tips to avoid mistakes:
- Review each income and expense invoice before including it in the return.
- Use a billing software like the one that has Asesoria Orihuela Costa to automate the calculations.
- Consult with an advisor to make sure the deductions are correctly applied.
3. Deduct unjustified expenses (Very important)
For an expense to be deductible, it must meet three requirements:
- Be related to economic activity.
- Have a valid invoice in accordance with the legislation.
- Be registered in the accounting of the business.
- Be necessary and exclusive in an obvious way, without a doubt for the development of the activity.
Frequent mistakes include deducting personal expenses or using tickets instead of invoices. To avoid this, classify your invoices well and use a separate bank account for business activity.
4. Not having a good accounting management
A disorderly accounting complicates the quarterly declaration and can cause errors in tax settlement. The ideal is to use management software or have comprehensive advice that helps you keep your accounting up to date.
Practical advice:
- Digitise all your invoices and documents.
- Keep your accounting books up to date.
- Schedule monthly reviews to avoid accumulation of errors.
5. Do not correct errors in previous statements
If you find an error in a declaration already submitted, you should first rectify the error as soon as possible by means of a supplementary declaration or a substitute declaration.
Rectifying self-assessment
But since the third quarter of 2024 it is very easy to correct a tax return through corrective self-assessment.
Now hacienda allows you to correct the error directly in the declaration and correct it.
If, for example, you have declared others, you no longer have to submit a letter requesting the rectification, you can do it in the same declaration.
Ignoring these failures can result in inspections or sanctions.
Learn how to rectify a tax return

Corrective self-assessment: how to easily correct tax errors
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Extra: the most common tax error
Many customers make the mistake of not providing invoices, but documents that are not valid to account for and declare them.
It is very typical to receive bank statements, proforma invoices, payments such as an invoice, tickets without any data, invoice without date, without customer data, even handwritten invoices in the 21st century.
But it is normal and we understand it because each of us is focussed and waiting to make money, not from accounting. Most freelancers or companies do not earn enough to have an accountant or administrative in the company and turn to us.
Why is good tax planning important?
Proper tax planning is key to avoiding unpleasant surprises with the Treasury. It is not only about complying with tax obligations, but also about optimising the tax burden of your business.
Benefits of strategic tax planning
Among the benefits of proper tax planning we highlight:
- Reduction of the tax burden: Apply deductions and bonuses efficiently.
- Prevention of sanctions: Complying with the regulations avoids fines and surcharges.
- Better financial forecast: Anticipating tax payments allows for better cash flow management.
To achieve these benefits, having the support of a tax advisor is essential, since an expert can analyse the situation of your business and find the best strategies to optimise your taxation.
Avoid tax errors with the help of Orihuela Costa Advisory

Avoiding these mistakes is key to good financial health and the fulfilment of your tax obligations. At Asesoría Orihuela Costa, we offer:
- Comprehensive advice for companies, SMEs and freelancers.
- Management and tax, accounting and labour advice.
- Tax filing without errors.
- Optimisation of your taxation to avoid sanctions and save money.
- Strategic planning to improve the financial management of your company.
Don’t risk the future of your business for a simple mistake.
Contact us and leave your statements in the hands of experts.