What Is a Treasure Bill?

The Safest Parking Lot for Your Money — Until Interest Rates Move

When the Federal Reserve raises interest rates, we usually hear about the painful side: mortgages get more expensive, car loans cost more, and stocks can fall.

But there is another side.

Savers suddenly get paid more.

One of the simplest places to see this is in U.S. Treasury bills (T-bills) — short-term debt issued by the U.S. government.

What Is a Treasury Bill?

Think of it this way:

You lend money to the U.S. government for a short period. In return, the government pays you interest.

Treasury bills mature in one year or less. The U.S. Treasury regularly issues T-bills with maturities such as:

Treasury securities with longer maturities are generally called Treasury notes or Treasury bonds, not T-bills.

How Do T-Bills Pay Interest?

T-bills traditionally work a little differently from a savings account.

Suppose you buy a Treasury bill that will pay you $100,000 at maturity.

You might pay approximately:

$98,000 today

and receive:

$100,000 at maturity

The difference represents your investment return.

In practice, Treasury auctions and quoted yields make the calculation somewhat more complicated, but the basic idea is simple:

Buy below face value → receive face value at maturity.

What Does the Federal Reserve Have to Do With This?

This is where things become interesting.

The Federal Reserve does not directly set the yield on Treasury bills.

Instead, it sets a target range for the federal funds rate and influences other very short-term interest rates through monetary policy.

Because T-bills are short-term investments, their yields tend to be closely connected to expectations for short-term interest rates.

Imagine the Fed starts raising rates:

Fed rate ↑ → short-term market rates ↑ → newly issued T-bill yields generally ↑

Suppose 3-month T-bills were yielding around 2%.

You invest $100,000.

Your annualized yield is approximately 2%.

Now imagine inflation becomes a problem and the Fed aggressively raises rates. New 3-month T-bills may eventually offer something closer to 5%.

Suddenly, the same $100,000 can generate approximately:

$5,000 a year annualized instead of $2,000.

That is why rising interest rates can actually be good news for people holding large amounts of cash.

But There’s a Catch

Suppose you bought an existing Treasury security yielding 2%.

Then market interest rates jump and newly issued comparable Treasuries yield 5%.

Why would another investor pay full price for your security yielding only 2% when a new security offers 5%?

They wouldn’t.

Your security’s market price must fall enough to make its effective yield competitive.

This produces one of the most important rules in bond investing:

Interest rates ↑ → existing bond prices ↓

Interest rates ↓ → existing bond prices ↑

However, the effect is generally much smaller for very short-term T-bills than for long-term Treasury bonds.

Why?

Because a 3-month T-bill is going to mature very soon. You can simply receive your money and reinvest it at the new higher rate.

A 20- or 30-year Treasury has much greater interest-rate risk because investors could be stuck with its lower coupon for decades.

What Happens When the Fed Cuts Rates?

Now reverse the situation.

Suppose short-term Treasury yields are around 5%.

The Fed begins cutting rates.

Over time:

Fed rate ↓ → short-term rates ↓ → new T-bill yields generally ↓

Your existing T-bill still matures normally, but when you try to reinvest the money, you may discover that the next T-bill yields only 4%.

Then 3%.

Perhaps eventually 2%.

This is called reinvestment risk.

Your principal hasn’t disappeared.

Instead, the income your cash can generate has fallen.

T-Bills vs. Long-Term Treasuries

This distinction is extremely important.

Suppose you expect interest rates to fall substantially.

A 3-month T-bill doesn’t lock today’s yield in for very long. After three months, you have to reinvest at whatever rates are available then.

A 10-year Treasury note, however, can lock in its coupon rate for years. And if market interest rates fall significantly, the market value of that existing Treasury can rise.

But the opposite is also true.

If interest rates unexpectedly rise, long-duration Treasuries can suffer substantial price declines.

So there is a trade-off:

T-bills = low duration risk, but high reinvestment risk.

Long-term Treasuries = greater duration risk, but the ability to lock in rates for much longer.

Why Investors Use T-Bills as a “Parking Lot”

Imagine you have $1 million but don’t want to put it into stocks immediately.

You are waiting for an opportunity.

Instead of leaving the money sitting in a checking account, you could hold Treasury bills.

If short-term Treasury yields were 4%, for example:

$1,000,000 × 4% ≈ $40,000 per year

before federal taxes, assuming comparable yields persisted.

Meanwhile, the money remains invested in short-term U.S. government obligations.

This is one reason investors sometimes describe T-bills as a parking lot for cash.

You can also gain convenient exposure to short-term Treasuries through Treasury-bill ETFs such as SGOV, BIL, or SHV, although ETFs behave somewhat differently from owning an individual T-bill until maturity.

One More Tax Advantage

Treasury interest is generally subject to federal income tax, but it is generally exempt from state and local income taxes.

That can make Treasuries particularly attractive to investors living in states with relatively high income-tax rates.

The Big Picture

Treasury bills aren’t exciting.

That’s precisely their appeal.

When interest rates rise, short-term Treasury yields generally rise, allowing savers to earn more.

When interest rates fall, T-bill yields generally fall, reducing the income available when the bills mature and the money is reinvested.

And unlike long-term bonds, short-term T-bills have relatively little sensitivity to changes in interest rates because they mature quickly.

So when you hear:

“The Fed raised interest rates.”

Don’t automatically think:

“Everything just got more expensive.”

For borrowers, that’s often bad news.

For savers holding cash?

The government may have just increased the rent it’s willing to pay to borrow your money.