IBKR Tax Return Guide – Step by Step

Interactive Brokers does not issue a German tax certificate. This means you must declare your capital income yourself in your tax return. The good news: With BubbleTax, this takes just a few minutes. Here's how the complete process works.

Why is there no IBKR tax certificate?

Interactive Brokers is headquartered in Ireland (IBKR Ireland Ltd.) and is not a German credit institution. Therefore, IBKR neither withholds flat-rate tax (Abgeltungsteuer) nor issues an annual tax certificate per § 45a EStG. You are required to declare your capital income yourself in Anlage KAP of your income tax return.

Note: This also applies to introducing brokers such as LYNX, CapTrader, BANX, MEXEM, AGORA Direct, or WH SelfInvest – they all use IBKR as their custodian bank. The only requirement for BubbleTax is the XML export of your account data.

The Process in 4 Steps

Set up Flex Query & Export XML

At IBKR, the data export is called a 'Flex Query'. You create an export template (a so-called Activity Flex Query) once, then run it for each tax year individually.

Navigate to Performance & Reports → Flex Queries → click the plus sign (+) next to 'Activity Flex Query' in the IBKR Client Portal. Setup takes about 5–10 minutes – after that, each additional export takes seconds.

Upload All XML Files to BubbleTax

Upload all exported XML files together via drag & drop. Important: Always upload all available years, not just the current tax year.

BubbleTax processes the data fully automatically: FIFO calculation per § 20 Abs. 4 EStG, EUR conversion at ECB daily rates, withholding tax crediting, and loss offsetting – usually in under a minute.

Review the Tax Report

The finished report shows all relevant amounts per tax year: gains, losses, dividends, interest, withholding tax, and advance lump sums – broken down by security and asset class.

The report includes a tax summary with direct line references for Anlage KAP, KAP-INV, and where applicable Anlage SO. Plus detailed tables for every single transaction.

Transfer Values to Your Tax Return

Transfer the values from the BubbleTax tax summary into ELSTER, WISO Steuer, SteuerSparErklärung, or your preferred tax software.

Each amount is assigned to a specific KAP line. You just need to type the values – no calculations needed.

Setting Up the Flex Query – Key Settings

When creating the Flex Query, you select which data to export. BubbleTax requires exactly seven data sections:

The 7 Sections

#	Section & Setting
1	Cash Report – with 'Currency Breakout' enabled
2	Complex Positions – no special setting needed
3	Statement of Funds – with 'Currency Breakout' enabled
4	Corporate Actions – select 'Detail'
5	Open Positions – select 'Summary'
6	Trades – select 'Execution' (not 'Order'!)
7	Transfers – select 'Transfer'

Important: In each section, all fields must be manually enabled – they are disabled by default at IBKR. Don't forget to save after each section.

Delivery Configuration

Format: XML
Period: Custom (selected during export)

General Settings

Date format: yyyyMMdd
Time format: HHmmss
Separator: ; (semicolon)

After registering with BubbleTax, you'll find a detailed guide with screenshots directly on the upload page.

The community has also documented the complete workflow as a step-by-step guide. privatsparer.de →

Export – What You Need to Know

Year-by-Year Export

IBKR limits the query period to 365 days. Run your Flex Query for each year individually (e.g., Jan 1 – Dec 31, 2024) and upload all XML files together to BubbleTax.

Export All Available Years

Don't just export the current tax year – export all available years (up to seven at IBKR). BubbleTax needs the complete purchase history to correctly calculate acquisition costs and FIFO. The most common error for new users: prior years are missing.

Include January of the Following Year

Also export at least January of the following year. Interest bookings at IBKR sometimes occur in early January but belong to the prior tax year under the 10-day rule (§ 11 EStG for recurring payments).

What Does the Tax Report Contain?

The BubbleTax report is structured so you can use it directly as documentation for the tax office:

Tax summary with line references for Anlage KAP, KAP-INV, and Anlage SO
Breakdown by asset class: stocks, ETFs/funds, options, futures, CFDs
Dividends, substitute dividends, interest, and securities lending
Withholding tax overview with creditable amounts
Corporate actions (splits, spin-offs, mergers)
Foreign currency gains and losses
Detailed tables with every single transaction
Open positions at the start and end of each year

Portfolio Transfers – Recording Acquisition Costs

If you transferred securities from another broker to IBKR, IBKR doesn't know the original purchase prices. BubbleTax provides an input form where you can record the acquisition costs per position.

Why this matters: Only the profit is taxed (sale proceeds minus acquisition costs). Without acquisition costs, the tax office must assume the entire sale amount is profit. In extreme cases, this can mean more tax than you actually earned.

Avoiding Common Mistakes

These are mistakes we regularly see from new users:

Only exported the current year – without prior years, BubbleTax cannot calculate the FIFO chain and acquisition costs
Exported CSV instead of XML – BubbleTax requires the XML export from the Activity Flex Query
Fields in sections not enabled – all fields are disabled by default at IBKR and must be manually checked
Selected 'Order' instead of 'Execution' for Trades – FIFO requires the execution level
Didn't export January of the following year – interest bookings may be missing

IBKR Tax Return – Guide