Today we’re going to see how easy it can be to file your Spanish income tax return when you trade with Interactive Brokers and use RentaXML. From downloading the broker’s report to the final summary with all the boxes ready for the AEAT (the Spanish tax agency) — all the steps in order, with the important details worth knowing if you have positions open from previous years.
Step 1: Download the Interactive Brokers report
The first thing is to go into the Interactive Brokers account management interface. If you trade from ProRealTime you have direct access within the platform. Once inside and with the account unlocked via two-factor authentication:
Download the activity CSV
Go to Performance & Reports and click on Statements
Select the account (or accounts if you have several)
On Activity Report click the blue arrow
For the period select Annual — 2025 will show by default
Click Download CSV
If the reports are very large, you’ll see a clock icon on the side indicating they’re being generated. When it disappears, they’ll be available to download.
Step 2: Create an account on RentaXML
Once you have the CSVs downloaded, go to rentaxml.com. The page has two options:
- I’m already a customer — if you’re already registered, you log in directly with your email and password
- Try for free with my file — to start from scratch, see the result and only pay if it convinces you
If you register for the first time, fill in your email and a password. I recommend ticking the box to subscribe to the newsletter — that’s where I send information about everything Campus Opciones. Afterwards you’ll receive a verification email. Important: check the spam folder if it doesn’t appear in your inbox. Once verified, log in.
Step 3: Create a file and upload the CSV
Select the tax year (2025 by default) and click Create file. Once inside, upload the 2025 CSV you downloaded from Interactive Brokers. The app will ask whether you also want to upload the reports from previous years — you can do it here or in the next step.
Once the file is uploaded, click Tax summary and then Calculate. The app processes the CSV, downloads the official exchange rates from the European Central Bank and applies all the necessary recalculations.
Step 4: Resolve tax issues
Before paying to unlock the file, you can see the summary with the data partially hidden. The important thing here is to go to the Tax Issues section to check that everything is correct.
The most common issue appears when there are trades that were opened in previous years. If you see them, simply upload the CSVs for the corresponding years and they’ll be resolved automatically. Once uploaded, the issues tab should be clean.
Step 5: Review the securities portfolio
If you want to see more detail on how each trade is being calculated, you can go to Securities Portfolio. There you see trade by trade: the buy, the sell, the options, the futures and how each one has been calculated with the ECB exchange rates applied day by day.
This is useful to check that the calculation is consistent with your real trading, especially if you combine options, futures, ETFs and dividends in the same account.
Step 6: Review the instructions for the AEAT
Before unlocking the file, go to Instructions. There you have the complete guide on how to fill in the return with your data: which boxes to use for stocks, ETFs, futures and options, how to declare dividends and interest, how to apply withholdings at source and how the two-month rule has been applied.
- Specific boxes of Form 100 according to your type of trading
- Dividends with withholdings and double deduction
- The two-month repurchase rule already applied
- Screenshots of the process on the AEAT website
Step 7: Unlock the file
If everything is correct, click Unlock file. It takes you to the payment gateway — a single payment of €45 per file, with no subscription or automatic renewal. If you have a discount code, you can apply it at this step.
Step 8: Access all the data
Once the file is unlocked you can see all the complete data: the tax summary with all the amounts, the detailed securities portfolio and the step-by-step guide on how to incorporate it all into the AEAT.
You can also download two formats:
- PDF — to review everything in a separate document or pass it to your accountant
- Excel — for any additional checks or manual calculations you want to do
Important disclaimer
Conclusion
The whole process is as simple as downloading your CSVs from Interactive Brokers, uploading them to rentaxml.com, resolving the tax issues (if any) and unlocking the file to have everything ready for the AEAT. What used to be a tedious process of hours with spreadsheets and manual conversions is now reduced to a few clicks. If you’re interested in starting to trade options from a convenient platform, take a look at ProRealTime — you have direct access to Interactive Brokers from the platform itself.
