# Cross-Currency Basis

> The cross currency basis measures deviations from covered interest parity. Learn why it exists, why it is often negative and what it says about dollar funding.

Source: https://learn.tradelabsai.com/forex/cross-currency-basis/  
Track: Forex · Level: Advanced · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Cross-Currency Basis", https://learn.tradelabsai.com/forex/cross-currency-basis/

The cross currency basis is the extra spread that must be added to one leg of a currency swap to make it fair at market prices. In a world where covered interest parity held perfectly, the basis would be zero. Since the 2008 financial crisis, it has often been significantly negative for many currencies against the US dollar, meaning that borrowing dollars through currency swaps costs more than interest rate differences alone suggest. The basis has become an important gauge of global dollar funding stress.

## Definition

In a cross currency basis swap, one party pays a floating rate in one currency and receives a floating rate in another, plus a spread (the basis) on the non dollar leg.

- **Negative basis (e.g. EUR/USD minus 20 basis points):** the party borrowing dollars via the swap effectively pays 20 basis points more than parity implies. Dollars are in demand.
- **Positive basis:** the reverse.

Equivalently, the basis shows up as a gap between the dollar interest rate implied by FX forwards and the actual dollar money market rate. See [FX Swaps and Currency Swaps](https://learn.tradelabsai.com/forex/fx-swaps-and-currency-swaps/) and [Covered and Uncovered Interest Parity](https://learn.tradelabsai.com/forex/interest-rate-parity/).

## Why the basis exists

If covered interest arbitrage were free and could be done at any size, any basis would be traded away. After 2008, several frictions prevent this:

| Friction | Effect |
|---|---|
| Bank balance sheet costs | Leverage ratio and capital rules make arbitrage trades costly for banks, especially at quarter ends |
| Strong demand for dollar funding | Non US banks, insurers and companies hedging dollar assets need dollars |
| Counterparty and credit risk | Lending in one currency against another carries risk |
| Limited arbitrage capital | Few players can deploy large amounts |

Research by economists at the BIS and others, including Du, Tepper and Verdelhan (2018), documented persistent CIP deviations and linked them to bank balance sheet constraints, with spikes around quarter ends.

**Example: The implied dollar rate**
Spot EUR/USD is 1.0850, and the 3 month forward is 1.0922. Three month euro rates are 3.00%. From covered interest parity, the implied 3 month dollar rate is:

(1.0922 / 1.0850) × (1 + 0.03 × 0.25) minus 1, annualised ≈ (1.006636 × 1.0075 minus 1) × 4 ≈ 5.67%.

If the actual dollar money market rate is 5.30%, borrowing dollars via the FX swap costs about 37 basis points more. That gap is (roughly) the cross currency basis, negative from the perspective of a euro holder seeking dollars.

## When the basis widens

- **Financial crises:** in late 2008, the basis for several currencies against the dollar widened to well over 100 basis points as banks scrambled for dollars.
- **March 2020:** the basis widened sharply as global firms hoarded dollars, until the Federal Reserve expanded central bank swap lines. See [The Federal Reserve and the FOMC](https://learn.tradelabsai.com/macro/the-federal-reserve-and-the-fomc/).
- **Quarter and year ends:** banks shrink balance sheets, temporarily widening short dated basis.
- **Strong hedging demand:** for example, Japanese investors hedging large US bond holdings push the USD/JPY basis more negative.

## Why it matters

| User | Why it matters |
|---|---|
| Global banks | Cost of dollar funding through swaps |
| Investors hedging foreign assets | Affects hedging cost and hedged returns |
| Corporate borrowers | Choice between borrowing in dollars or swapping from another currency |
| Policymakers | Indicator of funding stress and need for swap lines |
| Arbitrageurs | Potential returns from CIP trades if they have balance sheet capacity |

See [Systemic Risk](https://learn.tradelabsai.com/portfolio/systemic-risk/).

## Basis and hedged returns

When the basis is negative for a foreign investor buying US assets, hedging the dollar exposure back to their home currency is more expensive than interest differences alone. A Japanese insurer buying US Treasuries may find that, after hedging costs including the basis, the hedged yield is barely higher than Japanese government bonds, which affects global capital flows.

## Frequently asked questions

### What is the cross currency basis?

The spread added to one leg of a currency swap to make it fair at market prices, reflecting deviations from covered interest parity.

### Why is the cross currency basis negative?

Mainly because of strong demand for dollar funding and limits on banks' ability to arbitrage, which make borrowing dollars via swaps more expensive than parity implies.

### What does a widening basis signal?

Stress in dollar funding markets, often during crises or around quarter ends.

You have finished the Forex track. Continue with fixed income, starting with [How Bonds Work](https://learn.tradelabsai.com/bonds-credit/how-bonds-work/).

## Continue learning

- Previous lesson: [Covered and Uncovered Interest Parity](https://learn.tradelabsai.com/forex/interest-rate-parity/)
- Related: [Covered and Uncovered Interest Parity](https://learn.tradelabsai.com/forex/interest-rate-parity/): Interest rate parity links exchange rates and interest rates. Learn covered and uncovered parity, the arbitrage behind them and the forward premium puzzle.
- Related: [FX Swaps and Currency Swaps](https://learn.tradelabsai.com/forex/fx-swaps-and-currency-swaps/): An FX swap exchanges currencies now and reverses later; a cross currency swap exchanges interest payments for years. Learn both, their pricing and their uses.
- Related: [FX Forwards and Forward Points](https://learn.tradelabsai.com/forex/fx-forwards-and-forward-points/): An FX forward fixes an exchange rate for a future date. Learn how forward rates and forward points are calculated from interest rates, with examples and uses.
- Related: [Systemic Risk](https://learn.tradelabsai.com/portfolio/systemic-risk/): Systemic risk is the danger that problems at one firm or market spread through the whole financial system. Learn its channels, past examples and what traders can do.
- Related: [The Federal Reserve and the FOMC](https://learn.tradelabsai.com/macro/the-federal-reserve-and-the-fomc/): The Federal Reserve sets US monetary policy through the FOMC. Learn how meetings work, the dot plot, statements and press conferences, and how Fed days trade.