QE and QT Balance Sheet Mechanics Explained

Key Takeaways

• QE swaps longer-duration private-sector assets for overnight interest-bearing reserves; QT reverses that swap as Treasuries mature and the Fed does not reinvest.
• The SOMA peaked near $9 trillion in 2022; QT began June 2022 with monthly caps of $60 billion Treasuries and $35 billion agency MBS, later cut to $25 billion Treasuries in 2024.
• Reserves do not fall one-for-one with QT because ON RRP take-up and TGA changes absorb part of the drain, two balance sheets of equal size can produce very different funding conditions.
• MBS prepayments slow when rates rise, so actual monthly MBS runoff typically comes in below the $35 billion cap, making the portfolio shrink more slowly than Treasuries.

What It Is

Quantitative easing (QE) is the Fed creating reserves to buy Treasury securities and agency mortgage-backed securities (MBS) from the private sector. Quantitative tightening (QT) is the reverse: the Fed allows maturing securities to roll off its balance sheet without reinvesting the proceeds, so reserves shrink as the Treasury or agency repays principal.

The System Open Market Account (SOMA), managed by the New York Fed, holds the securities. At the 2022 peak the Fed's balance sheet stood near $9 trillion, up from about $4 trillion in early 2020 and below $1 trillion before the 2008 crisis. QT began in mid-2022 with announced monthly caps of $60 billion Treasuries and $35 billion agency MBS.

The Intuition

The Fed cannot buy an asset without creating a liability of matching size. When it buys a Treasury from a primary dealer, the dealer's bank receives reserves at the Fed, and those reserves are a Fed liability. So QE works by swapping a longer-duration asset held in the private sector for an overnight, interest-bearing claim on the central bank. Prices of the swapped assets, and anything priced off them, adjust.

QT unwinds that swap slowly. As Treasuries mature, Treasury pays the Fed with cash from its TGA. The Fed extinguishes the corresponding reserves. The private sector is left holding a new Treasury in replacement, issued to rebuild the TGA, so net Treasury supply to investors rises and reserves fall.

How It Works

Three balance sheets interact: the Fed's, the private sector's, and Treasury's. Simplified T-accounts for QE on a $10 billion Treasury purchase:

Fed                                    Private bank (aggregate)
+10 Treasuries                          -10 Treasuries
+10 Reserves (liability)                +10 Reserves (asset)

For QT on a $10 billion maturity that is not reinvested:

Fed                                    Treasury
-10 Treasuries (matures)                +10 new bills issued
-10 Reserves (liability)                -10 cash used to pay Fed (from TGA refill)

Private sector
-10 Reserves                            +10 new Treasury bills

The monthly caps determine the maximum runoff pace. If Treasury maturities in a given month exceed the cap, the Fed reinvests the excess. If MBS prepayments run below the cap, the shortfall is not made up with Treasury purchases; caps are maxima, not targets. The FOMC can and does adjust caps, as it did in 2024 when it slowed the Treasury cap from $60 billion to $25 billion to smooth the transition toward ample reserves.

Worked Example

In March 2020, the Fed restarted asset purchases at an unlimited pace. Between February and June 2020 SOMA holdings rose by roughly $2.8 trillion, from about $3.9 trillion to $6.7 trillion. Reserves plus ON RRP plus the TGA all had to rise by the same aggregate amount, net of currency changes, because Fed liabilities balance Fed assets.

In June 2022, the FOMC began QT. Monthly caps were phased in to $60 billion Treasuries and $35 billion MBS. Over the following two years, SOMA fell by about $1.7 trillion. Reserves did not fall by the full amount because the TGA rebuild after the 2023 debt-ceiling episode and a sharp decline in ON RRP take-up absorbed much of the drain. That is why two different balance sheets of the same size, one with high ON RRP and low reserves and the other with low ON RRP and higher reserves, can feel very different in funding markets.

Common Mistakes

1. Treating QE as money printing. Reserves are inside-money held by banks at the Fed. They do not circulate as deposits. QE can expand deposits indirectly through credit creation, but the direct effect is a duration swap in the private sector's portfolio.
2. Assuming QT reduces bank reserves one-for-one. Reserves only fall if the other two major Fed liabilities (ON RRP and TGA) are stable. In 2022 and 2023, ON RRP absorbed most of the runoff. In 2024 and 2025, the draining of ON RRP cushioned reserves again.
3. Ignoring MBS convexity. MBS prepayment speeds slow when rates rise, so actual monthly runoff often comes in well below the $35 billion cap. That makes the MBS portfolio shrink slower than the Treasury portfolio, a reason many at the Fed favor transitioning to an all-Treasury SOMA over time.
4. Conflating the balance sheet tool with the rate tool. The FOMC sets the policy rate via IORB and ON RRP. QE and QT influence the term premium and financial conditions at longer horizons. They are complementary, not substitutes.
5. Forgetting Treasury's role. Reserves only fall at maturity if Treasury actually pays cash to the Fed. That cash comes from new issuance to the private sector, which ties QT pace to debt management decisions that are made outside the Fed.

Frequently Asked Questions

What exactly happens to bank reserves when the Fed buys a Treasury under QE? The Fed credits the selling dealer's bank with new reserves equal to the purchase price. The dealer's balance sheet swaps a longer-duration asset for a short-term, interest-bearing claim on the central bank. Total reserves in the system rise by the amount purchased, and the Fed's balance sheet expands by the same amount on both sides.

Why don't reserves fall one-for-one during QT? Reserves are just one of three major Fed liabilities, the others are the TGA and ON RRP balances. When QT drains reserves, the ON RRP or TGA can simultaneously shrink, offsetting the impact on reserves. In 2022 and 2023, declining ON RRP balances cushioned reserves even as the SOMA shrank; in 2024 the TGA played a similar role.

What are the monthly QT caps and what happens if maturities fall short? The FOMC announced caps of $60 billion per month for Treasuries and $35 billion for agency MBS when QT started in June 2022. If actual maturities in a given month exceed the cap, the Fed reinvests the excess. If maturities fall below the cap, as MBS often does when prepayments slow, the shortfall is not made up with other purchases. Caps are ceilings, not targets.

Is QE inflationary? QE directly creates bank reserves, which are inside-money held at the Fed and do not circulate as deposits. The inflationary risk comes from second-order effects, lower long-term rates encourage borrowing and spending, not from reserves entering circulation. Research on the inflation impact of post-2008 QE showed modest pass-through; the 2020–2021 episode combined QE with massive fiscal transfers, which had a more direct demand-side effect.

Why does MBS runoff lag Treasury runoff during QT? Mortgage prepayments slow when mortgage rates rise, because fewer homeowners refinance or sell. When the Fed is tightening and rates are high, fewer mortgages in the SOMA prepay, so actual monthly runoff consistently comes in below the $35 billion cap. That is why the Fed's SOMA transitions toward an all-Treasury composition slowly even during active QT.

Sources

1. Federal Reserve Board. "Policy Normalization Principles and Plans." https://www.federalreserve.gov/monetarypolicy/policy-normalization.htm
2. Federal Reserve Board. "H.4.1: Factors Affecting Reserve Balances." https://www.federalreserve.gov/releases/h41/
3. Federal Reserve Bank of New York. "System Open Market Account Holdings." https://www.newyorkfed.org/markets/soma-holdings
4. Federal Reserve Board. "FEDS Notes: Research on Reserve Demand and Balance Sheet Policy." https://www.federalreserve.gov/econres/notes/feds-notes/

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.