Lombardkredit vs Box Spread: €100,000 Borrowing Cost Comparison
€100,000 over 12 months. Same borrower, same need, two different financing structures. Here is what each one actually costs in early 2026 — pre-tax, after-tax, and including the parts most comparison tables hide.
The headline numbers
| Item | Lombardkredit (Smartbroker) | Short box spread (ESTX50) |
|---|---|---|
| Posted rate | Euribor + 3.0% ≈ 5.20% | €STR + ≈10bp ≈ 2.10% |
| Gross interest, 12m | €5,200 | €2,100 |
| Tax treatment | Private interest, not deductible | Termingeschäft loss, offsettable |
| Tax shield (26.375%) | €0 | €554 |
| Net after-tax cost | €5,200 | €1,546 |
| Effective rate | 5.20% | 1.55% |
Rates indicative as of early 2026. Live numbers on the home-page curve. Smartbroker margin is a representative German broker — Comdirect Wertpapierkredit is similar; DKB and Consorsbank cluster around Euribor + 2–4%.
Where the money actually goes
The headline rate hides four cost layers. Here they are for both:
Lombardkredit
- Interest: €5,200 over 12m at 5.2%.
- Setup fee: typically €0 — most German brokers don't charge for the line itself.
- Hidden cost: nothing — the rate is the rate.
- Tax: nothing offsettable. Private-Schuldzinsenabzug is closed for capital-income use under Abgeltungsteuer.
Short box spread on ESTX50
- Implied carry: €2,100 (the €STR-anchored 12m rate × €100K).
- Commissions: ~€200 round-trip on Eurex for 50 contracts × 4 legs at ~€1/contract.
- Slippage: 0.05–0.20 points off mid on the combo. On a 200-wide box that's €5–€20 per contract; budget €100–€500 for a €100K position.
- Tax: the €2,100 carry is a Termingeschäft loss under §20 EStG. Post-JStG-2024 the €20K cap is gone, so it offsets against any other Kapitalerträge at 26.375%.
Add it up: box spread total cost ≈ €1,546 (after tax) + €200 commissions + ~€300 slippage ≈ €2,046. Still less than half the Lombardkredit even after the friction.
What changes the picture
The €1,546 number assumes you have at least €2,100 in offsetable Kapitalerträge that year. If you don't, the €554 tax shield doesn't materialise immediately — the loss carries forward, and the year-one cost stays €2,100. The Lombardkredit number is unconditional; the box spread number is conditional.
What changes the rate itself
The Lombardkredit rate floats with Euribor — when the ECB moves, your bank moves. The box-spread rate floats with €STR — same direction, different transmission. The 3% spread that Smartbroker charges is sticky; €STR-tracked instruments transmit more cleanly.
Concretely: a 100bp ECB cut next year would drop the Lombardkredit roughly 100bp. The box rate would drop similar size, but the gap between them generally widens in falling-rate cycles (term-funding markets price ahead of bank desks).
When the comparison flips
Two scenarios where a Lombardkredit can win:
- Small loan, short tenor. Below ~€25K, box-spread commissions and slippage eat the rate advantage. Below 3 months, you can't reach a clean Eurex expiry.
- No options account. If you're on a neo-broker and don't want to onboard with IBKR / CapTrader / LYNX, the Lombardkredit is the only line you can actually pull.
Try your own number
Pick a tenor and an amount on the calculator. The numbers above use today's curve; yours will too.