Money market fund or treasury bill: which should your savings sit in?

You have done the difficult part. There is money set aside that you are not going to spend this month, and you have accepted that leaving it in a current account is a slow loss.

So you ask where to put it, and you get two answers. A treasury bill. Or a money market fund.

Both get called safe. Both pay more than your bank. And almost everybody chooses between them by trying to work out which one is safer, which is the wrong question, because the honest answer is that they are close enough not to be the deciding factor.

The question that actually decides it is when you need the money back.

What each one is

A treasury bill is a loan you make to your government for a fixed stretch of time, at a return agreed the day you buy it. You hand over money now, you get a known amount back on a known date. If you want the mechanics of how the pricing works and how to buy your first one, that is covered properly here.

A money market fund is a pot that many people's money goes into together, run by a manager who uses it to buy a spread of short term debt. You own units in the pot, the value of your holding creeps up as the debt pays out, and you can usually ask for your money back within a few working days.

The fact that reframes the choice

Here is what nobody mentions when they present these as opposites.

A money market fund often holds treasury bills. Frequently a great many of them, alongside short term bank deposits and similar instruments.

So this is usually not a choice between lending to your government and taking a risk with somebody clever. You may well be buying the same underlying thing either way. What differs is the wrapper: one you hold directly with a fixed end date, the other someone manages for you with no end date and a fee.

Which is why "which is safer" gets you nowhere, and why the four differences below are the ones to think about.

The four things that actually differ

Access. This is the big one. A treasury bill is committed until it matures. In many countries you can sell one early, but you sell at whatever the market will pay that day, which may be less than you would have received by waiting. A money market fund lets you withdraw on request, typically landing within a few working days, though it varies by fund and country.

Certainty. A treasury bill's return is fixed the moment you buy. You know the exact amount and the exact date, which is unusual and genuinely valuable. A fund's yield floats: it moves as the things it holds mature and get replaced, so what it paid last year tells you something, but not what it will pay you.

Effort and minimums. Buying a bill means going through a bank, broker or platform, on a date the auction happens, with a minimum amount that can be substantial. A fund is usually easier to enter, often with a much smaller minimum, and topping it up is a transfer rather than an event.

Fees. A fund is run by people who charge for running it, taken out of the returns. That is not a scandal, it is the price of the convenience and the spread. But check whether a quoted yield is before or after that fee, because those are different numbers and both get advertised.

Which one, for what

The decision comes down to two questions about your own money.

Do I know the exact date I need this? Then a treasury bill, chosen to mature just before that date.

School fees due in six months. A rent renewal you have had the letter for. An insurance premium every January. These are known bills with known dates, and matching a bill's maturity to the date is the neatest thing in personal finance: the money is untouchable until roughly when you need it, which is a feature, and you know today exactly how much will arrive.

Might I need it at no notice? Then a money market fund.

Your emergency fund is the clearest case. Its entire purpose is to be there when something happens that you did not schedule, and money locked in a bill that matures in two months is no use to a person whose car died today. The slightly lower certainty is the price of being reachable, and for that money it is worth paying.

And if you are honestly not sure? A fund. Uncertainty has a cost, and paying it with a little flexibility is cheaper than locking money away and then having to break the lock at a bad price.

The middle option nobody explains

You do not have to choose once for everything.

If you have a lump sum and you want both the fixed return and some access, split it. Buy a 91 day bill this month, another next month, another the month after. From then on you have one maturing every month, so there is always money coming free soon without everything being committed to the same date.

It is called a ladder, it takes three months to build, and it is the standard answer to "I want it locked but not all of it locked".

Low risk is not no risk

Worth being straight about this, because both of these get described in a way that suggests certainty.

A treasury bill is about as safe as anything available in its own currency, since it is your government's own promise. What it cannot protect you from is inflation: a bill paying less than prices are rising is a loss in real terms, and a guaranteed one at that.

A money market fund is low risk, not risk free. It is not a bank account, its value can fall, and in genuinely stressed markets funds have occasionally frozen withdrawals or lost a little capital. Rare, and not a reason to avoid them. But it means the word "safe" is doing some work, and it is worth knowing what a fund holds rather than only what it yields.

Neither is necessarily covered by whatever deposit protection exists in your country. That is a question worth asking directly.

And if anybody offers you something described as a money market fund paying far above what others pay, the extra is not free. It is being paid for by risk somebody is not telling you about.

Neither one is for long term money

Both of these are for money you will need within a couple of years. They are not where a retirement pot or a ten year plan belongs, because their whole design is to hold value safely for a short stretch, and over long periods safety loses to inflation.

Money you will not touch for a decade has a different job to do, and its greatest advantage is time, which these instruments are not built to use.

The habit worth building

Stop asking which one is safer. Ask when you need the money.

Every time you set money aside, put a date on it, even a rough one. Next month. Six months. Not sure. Sometime after I am fifty. The date chooses the home almost by itself, and matching the two is most of what people mean when they talk about being good with money.

If you use Wealthpadi, the rates screen shows current treasury bill and money market rates side by side, which is a fairer comparison than whichever one somebody happened to mention to you. Rates move, so read them on the day rather than trusting a number from an article, including this one, which is why there are no rates quoted here.

This is one term from the plain English money glossary.

Put this into practice

Wealthpadi turns habits like these into something automatic. Track your money, set goals, and watch your net worth grow. Free to start.