Open market operations (OMOs) are transactions in which a central bank buys or sells government securities, or lends and borrows against them, in dealings with banks and other market participants. Their purpose is to change the amount of reserves in the banking system so that short-term interest rates stay close to the central bank's policy rate. OMOs are the routine, day-to-day tool of monetary policy in most countries.
The phrase "open market" means the central bank deals at market prices with a group of counterparties, rather than lending to the government directly or ordering banks to act. OMOs sit beside the other two classic tools, standing facilities (such as a discount rate window) and reserve requirements. Large-scale asset purchases, known as quantitative easing (QE), are open market operations on a much bigger scale with a different aim.
Open market operations in plain terms
Picture the central bank as the manager of a water tank that feeds every bank in town. If the water runs low, rates for borrowing it go up; if it overflows, they fall. The central bank keeps the level right by pouring water in or draining it out each day.
It pours water in by buying government bonds from banks, or by lending to them for a few days against bonds, paying with fresh central bank money. It drains water out by selling bonds or by borrowing banks' spare cash for a few days. The bonds are just the bucket; the point is the level of the tank, which sets the price of overnight money.
How OMOs work
A central bank forecasts how much liquidity banks will need, taking account of government payments, cash withdrawals and foreign exchange reserves operations, then runs auctions to close the gap. Operations come in two broad forms:
- Temporary operations. The central bank lends cash against securities for a fixed term, from overnight to a few weeks, through a repurchase agreement (repo), or absorbs cash through the reverse transaction. These are reversed automatically at maturity and are the most common type.
- Outright operations. The central bank buys or sells securities permanently, changing the size of its balance sheet and the stock of Reserve Money (M0) for longer.
Counterparties are usually banks and primary dealers. Collateral is mostly government paper such as Treasury Bills (TBs), with a haircut to protect the central bank against price falls.
OMOs in major economies
The US Federal Reserve's Open Market Desk at the Federal Reserve Bank of New York conducts operations on the instructions of the Federal Open Market Committee, which sets the target range for the federal funds rate. Since the 2008 crisis the Fed has operated with abundant reserves, steering rates mainly through the interest it pays on reserves and through standing repo and reverse repo facilities, so routine OMOs play a smaller role than before. The European Central Bank runs main refinancing operations and longer-term refinancing operations, lending to banks against eligible collateral, alongside outright asset purchase programmes.
Open market operations in Pakistan
The State Bank of Pakistan (SBP) uses OMOs to keep the weighted-average overnight repo rate close to its policy rate, inside a corridor bounded by its overnight reverse repo ceiling and repo facility floor, each set 100 basis points from the policy rate. Injections are usually reverse repo auctions against Market Treasury Bills (MTBs) and Pakistan Investment Bonds (PIBs), with tenors from a few days to a few weeks; mop-ups take cash out when the system has a surplus. The SBP also carries out outright purchases and sales.
Since December 2021 the SBP has offered Shariah-compliant, Mudarabah-based OMO injections for Islamic banks, backed by Ijara Sukuk and other Shariah-compliant securities, so that Islamic banking institutions can access liquidity without interest-based repo.
Pakistan's OMOs have grown very large because the government borrows heavily from scheduled banks, which then need SBP funding to carry the securities. According to the Pakistan Economic Survey 2024-25, average outstanding OMOs (excluding outright operations) were about Rs 11.3 trillion during July–March FY2025, up from about Rs 9.8 trillion in FY2024 and Rs 1.3 trillion in FY2021. Critics argue that such heavy, continuous injections blur the line between liquidity management and monetary financing of the budget.
Limits and debates
- Transmission. OMOs move overnight rates reliably, but how far that reaches KIBOR, deposit rates and lending rates depends on competition and bank balance sheets.
- Collateral scarcity. Where government securities are scarce or concentrated, operations can distort bond prices.
- Fiscal links. When central bank lending mostly funds banks' holdings of government debt, monetary and government borrowing decisions become entangled.