Overnight Rate

The overnight rate (also called the overnight lending rate or overnight interbank rate) is the interest rate at which banks and financial institutions lend money to each other for a one-day (overnight) period. This rate is the most fundamental interest rate in any financial system, serving as the anchor from which virtually all other interest rates in the economy are derived, including mortgage rates, corporate borrowing costs, savings account yields, and — critically for forex traders — currency swap rates.

Central banks use the overnight rate as their primary monetary policy tool:

• Federal Reserve (U.S.): Targets the federal funds rate — the rate at which depository institutions lend reserve balances to each other overnight
• Bank of Canada: Sets the overnight rate target within a 50 basis point operating band
• Bank of England: Targets the Bank Rate as its key overnight rate
• European Central Bank: Sets the deposit facility rate and main refinancing rate
• Bank of Japan: Targets the uncollateralized overnight call rate

When a central bank raises the overnight rate, it increases the cost of short-term borrowing throughout the economy, tending to slow economic activity and reduce inflation. When it lowers the rate, borrowing becomes cheaper, stimulating spending and investment. This transmission mechanism is the foundation of conventional monetary policy.

For forex traders, overnight rates are critically important for several reasons:

• Interest rate differentials between two countries' overnight rates are the primary fundamental driver of exchange rate movements over medium-term timeframes. Higher rates attract capital inflows, strengthening the currency
• Swap/rollover rates: The overnight cost or credit applied to forex positions held past the daily rollover time (typically 5:00 PM New York time) is directly derived from the overnight rate differential between the two currencies in the pair
• Forward pricing: Forward exchange rates are calculated using overnight and term interest rate differentials
• Carry trade profitability: Carry trades exploit the difference between high and low overnight rates across countries

Expectations about future overnight rate changes are arguably more important for forex markets than the current rate level. Currency pairs can move hundreds of pips in response to central bank decisions or even subtle shifts in language about future rate policy (forward guidance). Tools like the CME FedWatch tool track market expectations for future Federal Reserve rate decisions, and significant shifts in these expectations trigger immediate forex market reactions.

The overnight rate market itself is enormous — the Federal Reserve's overnight reverse repo facility alone regularly handles over $2 trillion in daily transactions. This massive market ensures that the overnight rate remains the most liquid and transparent interest rate in any economy, providing a reliable foundation for the entire interest rate structure.