Your German tax return
for Interactive Brokers
Figures done, lines assigned.
Interactive Brokers, LYNX, CapTrader and other introducing brokersFor private investors with an account at Interactive Brokers, CapTrader or another IBKR-based broker. You upload the Flex Query export, BubbleTax calculates FIFO, dividends, options, funds and foreign currency and puts every value on its line in Anlage KAP, KAP-INV or SO. Viewing is free, you pay only afterwards.
An e-mail address is all it takes. No payment details, no broker login.
| Line | Description | Amount |
|---|---|---|
| Anlage KAP | ||
| 19 | Foreign capital income | €23,482.65 |
| 20 | Gains from the sale of shares included in lines 18 and 19 | €76,360.01 |
| 22 | Losses other than losses from the sale of shares | €4,407.53 |
| 23 | Losses from the sale of shares | €53,779.30 |
| 41 | Creditable foreign taxes not yet credited | €43.36 |
| Anlage KAP-INV | ||
| 08 | Distributions from other investment funds (before partial exemption) | €16.51 |
| 26 | Gains and losses from the sale of fund units, other investment funds (before partial exemption) | −€111.56 |
Cooperations with four introducing brokers:
Tax report software for Interactive Brokers, CapTrader and other IBKR-based brokers
BubbleTax is tax report software for German private investors with an account at Interactive Brokers or an IBKR-based broker such as CapTrader, LYNX, Estably, MEXEM, WH SelfInvest, AGORA direct or ProRealTime. The software reads the broker's Flex Query export and turns it into tax-ready reports and values for the German tax return, including Anlage KAP, KAP-INV and SO. It covers stocks, ETFs and funds, dividends, options, futures, CFDs, foreign currencies, withholding tax and the Vorabpauschale. Disposals are matched under FIFO, every conversion uses the ECB rate of the respective day.
Over 3,000 registered users, over 2,000 tax reports sold, cooperations with four introducing brokers: MEXEM, WH SelfInvest, AGORA direct and ProRealTime.
As of September 2026. Fund data from WM Datenservice, the same source banks work with.
Three steps, one report.
No account linking, no login credentials for your brokerage account, no Excel.
Set up the Flex Query.
One click in IBKR; our guide walks you through every field. It is also available as a video.
Upload the XML.
Several tax years and up to two accounts in one run. We check right away whether periods are missing and tell you which ones.
Check the result, then buy.
You see the calculated values in the free preview. Only then do you pick a plan and download the full report as a PDF.
The special cases are the reason you are here.
One calculation engine for everything that occurs in an account at Interactive Brokers, CapTrader or another IBKR-based broker. No second file, no manual rework.
- Stocks and dividends.
- Every sale is matched under FIFO to the corresponding purchase, with acquisition cost and the ECB rate of the original transaction. Dividends are grouped by country, with withholding tax deducted and the creditable portion.
- Options and futures.
- OPT, FOP and FUT are assigned under the special rules for forward transactions, across year boundaries.
- CFDs and forex CFDs.
- Their own instrument classes, not reinterpreted as stock trading.
- Foreign currency gains.
- FIFO across your account movements in foreign currency, not across your securities holdings.
- Corporate actions.
- Splits, spin-offs and mergers are recognised and carried into the acquisition costs of the successor position.
- Funds, ETFs and Vorabpauschale.
- Classification under the German Investment Tax Act including partial exemption per fund type. The Vorabpauschale is calculated for accumulating funds; amounts already taxed are credited.
- Withholding tax.
- Credited under the applicable double taxation treaty, with the applicable caps.
- Several tax years, several accounts.
- FIFO runs consistently across all years, including account transfers with acquisition data.
What investors say who tried it differently before.
„For years I have been trying to solve the tax problem with foreign capital income at Interactive Brokers. I hired a tax advisor and had a professional check done. The results were not satisfactory. After the BubbleTax tax report, for the first time I had the feeling that the documents were plausible and consistent.“
„Amazing customer service and support, reports were generated promptly.“
Tax return with CapTrader, LYNX or directly at Interactive Brokers: one file, one report.
BubbleTax processes trading data from Interactive Brokers and IBKR-based brokers such as CapTrader, LYNX, Estably, MEXEM, WH SelfInvest, AGORA direct and ProRealTime. All of them run on the same trading platform and deliver the same Flex Query export, so the tax report is the same for each of these brokers.
German tax return with CapTrader as a private investor
As an IBKR-based broker, CapTrader does not withhold German capital gains tax and does not issue an annual tax certificate under German law. If your account is at CapTrader, you report your capital income in the tax return yourself: gains and losses from stocks, ETFs, options and futures, dividends with withholding tax, foreign currency gains and the Vorabpauschale for funds.
BubbleTax is the tax software for that: you export the Flex Query from your CapTrader account, upload the XML file and receive a German tax report with the values for Anlage KAP, KAP-INV and SO. That is how you do the CapTrader tax return yourself, without filling in spreadsheets by hand. The preview is free.
Not calculating for yourself?
The same calculation engine carries two more paths: tax firms bill their client work through it, brokers hand their German customers a finished tax report.
For tax firms
Create clients, upload Flex Query exports, receive traceable reports. You get access within one business day.
For brokers
Every spring your German customers need a tax report the tax office accepts. From a referral with a discount code to an embedded solution in your customer portal. Four introducing brokers already recommend BubbleTax: MEXEM, WH SelfInvest, AGORA direct and ProRealTime.
What BubbleTax cannot do.
So you know where you stand beforehand.
- We do not transmit anything to the tax office. There is no ELSTER interface. You enter the values yourself or hand the report to your tax firm.
- We do not give advice. BubbleTax calculates and documents. The software must not and does not intend to replace individual tax advice.
- We do not check your data for completeness we cannot see. If a period is missing from the export, we tell you. If a whole account is missing, we cannot know.
- We do not decide the partial exemption category for you. We classify automatically and conservatively based on WM Datenservice data. If you deviate, you carry the justification.
- We are neither a portfolio nor a trading application. BubbleTax reads only the Flex Query export, never your brokerage account.
- Your review is still required. The report discloses every calculation step so you can check it. We do not take that check off your hands.
The six questions before the first upload.
All further questions are on the FAQ page, sorted by topic.
What exactly do I need to export from Interactive Brokers?
A FlexQuery file (XML) from the Interactive Brokers portal. We show you step by step how to export it.
Can I see the result before I pay?
Yes. After the upload, BubbleTax runs the full calculation and shows you the calculated values in the free preview, without payment details. Only when you want to download the full report as a PDF do you choose a plan.
Does the tax office accept this report?
The report discloses every calculation with its legal basis so you can substantiate it towards the tax office. Nobody can promise that a tax office will accept a report, and neither can we. For complete documentation, we recommend submitting the BubbleTax report along with the corresponding account statements or broker documents.
I have options, futures and foreign currency in my account. Is one report enough?
Yes. One report covers everything that occurs in an IBKR account: stocks, ETFs, options, futures and CFDs under FIFO, foreign currency gains and losses from interest-bearing currency accounts, dividends with withholding tax, and funds with partial exemption and Vorabpauschale. Every value sits on the line of Anlage KAP, KAP-INV or SO where it belongs.
What happens to my data after the download?
Your files and reports stay encrypted in your account until you delete them or delete your account. Under "My data" you can see at any time what is stored and export or delete it. Transmission and storage are encrypted.
Can I process two different account holders with BubbleTax?
Yes. In the Pro version, you can process two completely independent IBKR accounts – even if they belong to different people. Important: Only if assets have been transferred between both accounts should you calculate them separately.
Have it calculated first, then decide.
The preview costs nothing and needs no payment details. Without a tool this is several hours of manual work in Excel, at a tax advisor quickly several hundred euros in fees, every year. BubbleTax calculates, your tax advisor reviews.
Start free preview