Funding rate arbitrage: how cash-and-carry trades work

The core idea

The structure consists of two opposing exposures with approximately equal notional:

• Spot leg. A spot position creates positive asset exposure.
• Perpetual leg. An equal-notional short perpetual creates offsetting derivative exposure.

When the two legs are closely matched, gains in one leg can offset losses in the other, reducing directional exposure. Funding is then one remaining cash-flow component: with positive funding, long perpetual holders pay short perpetual holders; with negative funding, the direction reverses. The mechanism is described in the funding-rate guide.

Why funding cash flows can arise

Perpetual contracts can trade above or below spot as positioning becomes imbalanced. Funding transfers are designed to create an economic incentive that helps keep the perpetual contract near its reference index. The sign and magnitude of funding can change at each interval and do not constitute a promised return.

Where the real risk sits

"Market-neutral" describes the trade's exposure to price direction — it does not mean risk-free. The actual risks are real and worth naming plainly:

• Funding can flip negative. If sentiment shifts and shorts start paying longs instead, this trade starts paying out rather than collecting — and rates can flip faster than a position can be unwound cleanly.
• The two legs aren't perfectly matched in practice. Spot and perpetual prices can diverge briefly (basis risk), and closing both legs at exactly the same moment isn't guaranteed, especially in fast markets.
• Margin and liquidation risk on the futures leg. The short perpetual leg typically runs on margin. A sharp price spike can put that leg under margin pressure even though the spot leg is gaining — a timing mismatch (margin calls happen faster than spot gains can be realized and moved over) that has caught traders out before.
• Exchange and counterparty risk. Holding assets and open positions on an exchange carries the exchange's own operational and counterparty risk, on top of the trade's market risk.
• Fees eat into thin margins. Funding rates are usually small; trading fees on both legs, especially if the position is opened and closed repeatedly, can offset a meaningful share of what funding pays.

A simplified example

Hypothetical example: a $10,000 spot exposure paired with a $10,000 short perpetual exposure at +0.01% funding per 8-hour interval produces a modeled $1 funding receipt per interval on the short leg, before fees, basis changes, slippage, margin effects and funding-rate changes. Three identical intervals would arithmetically equal $3; this illustrates the formula rather than a trading plan. The funding calculator performs the same arithmetic from user-defined inputs.

Key takeaway

Cash-and-carry combines offsetting spot and perpetual exposure so that directional sensitivity can be lower than either leg alone. Funding is only one component of the result; basis, fees, slippage, margin requirements, funding changes and counterparty risk remain. A displayed funding rate is a current market observation, not a forecast or guaranteed yield.