Can Box Spread Costs Offset Capital Gains in Germany? Ask Your Steuerberater
Short answer: under current German tax law, the carrying cost of a box spread is treated as a Termingeschäft loss and is offsetable against other Kapitalerträge at the Abgeltungsteuer rate of 26.375%. The detail is more complicated. Nothing here is tax advice — it's an explanation of where the law stands, the questions a Steuerberater can confirm for your case, and the documentation you should keep.
Where the law sits in 2026
Three pieces matter:
- §20 Abs. 1 Nr. 11 EStG classifies gains and losses from Termingeschäfte (forward / option transactions) as Kapitalerträge.
- §20 Abs. 6 EStG contains the loss-offset rules. Pre-2024, Satz 5 capped Termingeschäft losses at €20,000 per year for offset against other Kapitalerträge — a hard ceiling that the Bundesfinanzhof flagged as constitutionally problematic (BFH-Beschluss VIII B 113/23).
- Jahressteuergesetz 2024 (passed late 2024) retroactively struck Satz 5. The €20K cap is gone; full Termingeschäft loss offset against Kapitalerträge is restored, going forward and backward.
This means box-spread carrying costs (the difference between the credit you receive at entry and the fixed amount you owe at expiry) are treated as Termingeschäft losses. They reduce your Kapitalerträge for the year, which lowers your Abgeltungsteuer bill at 26.375% (incl. Solidaritätszuschlag).
What this looks like on a tax return
If you are a German tax resident, your broker reports your derivative gains and losses on the standard Steuerbescheinigung. IBKR (and resellers like CapTrader, LYNX) issue a Jahressteuerbescheinigung that breaks out:
- Kapitalerträge (dividends, interest, realised stock gains)
- Termingeschäftsgewinne / -verluste
- Offsettable amounts
If your broker is non-German (no Steuerbescheinigung), you file the figures yourself in Anlage KAP. A Steuerberater is highly recommended for this — the line items have to match the German categorisation, not the foreign broker's.
What is still uncertain
Three areas where reasonable Steuerberater might disagree, and where you should get a written opinion if the numbers are large:
- Carry-forward of losses. If you have no Kapitalerträge in the year, the loss carries forward. The mechanics of how a Termingeschäft loss carry-forward gets used in subsequent years is well-established but worth confirming for your specific brokerage account structure.
- Treatment in joint assessment (Zusammenveranlagung). Whether one spouse's box-spread loss can offset the other's Kapitalerträge depends on how the brokerage account is held and how the Anlage KAP is filed. Talk this through.
- Future legislative risk. JStG 2024 fixed the €20K cap retroactively, but tax law is not frozen. A future legislator could re-cap or re-classify. Your historical positions are governed by the law in force in the year of realisation.
Documentation you should keep
- Trade confirmations for the four legs (broker statement, ideally as PDF or screenshot).
- Combo ticket showing the box was placed as a single complex order.
- Computation of implied rate (calculator output, screenshot of the curve as-of date).
- Steuerbescheinigung at year-end. Cross-reference to your Anlage KAP entries.
- If your broker is non-German, a copy of the foreign broker's annual statement plus your own derivation of the German categorisation.
Why this section is not advice
Tax outcomes depend on facts we don't know — your other income, your residency timeline, your spouse's filing posture, your existing loss carry-forwards, the exact legal characterisation by your local Finanzamt. A 30-minute conversation with a Steuerberater who knows derivatives is worth more than any general guide. We have a separate piece on what to ask if you need a checklist.
The bottom line
Yes — box-spread carrying costs offset Kapitalerträge under the law as it stands in 2026. The headline savings of ~26% of the carry are real, contingent on you having offsetable gains. Get the documentation right, and treat the offset as the well-supported but not unconditional benefit that it is.
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