Money Market Funds for Corporate Treasury

A money market fund pools your cash with everyone else's into a diversified portfolio of short-dated, high-quality instruments, and gives you back same-day or next-day liquidity plus a modest yield. For corporate treasury it is one of the most common homes for operating and reserve cash — a rated, transparent, professionally managed vehicle that sits neatly inside the security-then-liquidity-then-yield discipline. It earns its place not by paying the most, but by preserving capital and staying liquid while it does. Reach for it the other way round and it will teach you the difference the hard way.

(This is general education on how corporate treasury uses these funds, not investment advice — the point is the treasury lens, not a recommendation for any specific situation.)

What a money market fund actually is

Start from the short-term investment basics: once you have surplus cash and a policy, you need somewhere to put it. A money market fund (MMF) is one option — a collective fund that invests in the money markets, meaning very short-dated, high-quality instruments: government paper like Treasury bills, repurchase agreements (repo), commercial paper (CP), and certificates of deposit (CDs). You buy units in the fund rather than the underlying paper directly, and in return you get diversification, professional management, and typically same-day or next-day access to your money.

The appeal for treasury is that it does three jobs at once. It puts idle cash to work at a yield. It keeps that cash liquid. And it spreads the underlying credit across many issuers instead of parking it all with a single bank. For a treasurer whose real job is preserving operating cash rather than growing it, that combination is exactly the right shape.

The main types

Not all MMFs sit in the same place on the risk spectrum, and the distinction matters more than the marketing sometimes suggests.

• Government / treasury funds hold government paper and government-backed repo. This is the lower-risk end: the underlying credit is about as good as short-term paper gets, and the yield reflects that. When capital preservation is the whole point, this is usually where it starts.
• Prime funds can also hold high-grade corporate instruments — CP and CDs from banks and companies. That broader universe typically pays a little more, but "a little more yield" is never free: it comes from taking a little more credit and liquidity sensitivity. In the US there are also municipal funds that hold short-dated municipal paper, relevant mainly for their tax treatment.

Cutting across those categories is the NAV distinction. Some funds aim to hold a stable, constant net asset value (CNAV) — a unit is worth what you paid, and you think of it like cash. Others carry a variable NAV (VNAV) that moves, however slightly, with the value of the underlying holdings. The stable-NAV label is convenient, but it is worth remembering it is an accounting and structural feature, not a guarantee that value can never move.

Why treasury reaches for them

Set MMFs against the alternative — leaving large balances sitting in bank deposits — and the case is straightforward:

• Diversification away from bank concentration. A big operating balance in one bank is a single point of failure. An MMF spreads the same cash across many high-grade issuers, which is the same instinct behind counterparty and concentration limits applied through a single instrument.
• Same-day or next-day liquidity. Used well, the cash is still there when the business needs it — which is the entire second priority of corporate cash investment.
• Professional management and transparency. Someone whose full-time job is the money markets manages the portfolio, and a rated fund publishes what it holds. You are not stock-picking short-term paper yourself.
• A rated vehicle. MMFs are typically highly rated (top money-market ratings such as the AAA-equivalent scales the agencies use), which gives policy a clean, checkable line to write against.

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A money market fund lets you optimise two of yield, safety and liquidity — never all three. Decide which two the cash needs before you decide which fund it goes into.

That triangle is the honest frame. Every MMF is a specific answer to it, and the answer that pays the most is, by construction, giving something up on one of the other two.

The treasury lens: it lives inside the policy

None of this is a licence to hunt for the best-yielding fund. MMF use belongs inside the investment policy, not alongside it. The policy should name which funds are permitted, set a rating floor, and cap concentration — both per fund and, looking through the fund, per underlying issuer — so that "diversification" doesn't quietly recreate a concentration you can't see. This is the same governance that runs through debt and investment management: the instrument changes, the discipline doesn't.

The reason the order is fixed is the reason it is always fixed for operating cash. You are investing money the business needs to run — payroll, suppliers, debt service. So the point of putting it in an MMF is capital preservation and liquidity first, and yield last, as the bonus you take only after the first two are satisfied. A fund that pays more but can't be redeemed on the day you need it has failed at the only two things that actually mattered.

The risk reality

Here is the part the fact sheet underplays: "cash-like" is not "cash." A money market fund is an investment. It is a very conservative, highly rated, short-dated investment — but it is not a guaranteed deposit, and it can face stress. Funds have, in the past, come under real pressure when the short-term markets they invest in seized up. The 2008 experience is the reference point, and the regulatory reforms that followed — the SEC's reforms in the US, the Money Market Fund Regulation in the EU — exist precisely because that risk turned out to be real when it had been treated as theoretical. I won't put numbers on the specific thresholds or tools those reforms introduced, because they've been revised and the details vary by jurisdiction; the point that matters for a treasurer is simpler: the reforms happened, which tells you the risk was never zero.

Which leads to the one habit worth building: read what the fund actually holds. Government or prime? What's the maturity profile? Who are the underlying issuers, and does the fund's concentration blow through the limits your own policy sets? A fund is not a black box you rate once and forget; it's a portfolio you can look through, and looking through it is the difference between managing the risk and hoping it isn't there. This is where MMFs connect to broader liquidity risk management: the fund is only as liquid as the paper inside it on the day everyone wants out at once.

Docs vs reality

On paper, MMFs are the easy button — cash-like, highly rated, liquid, done. In reality, the trap is dependably the same one. A treasurer under pressure to make the cash earn more reaches for the highest-yielding fund on the list, ticks the "AAA-rated" box, and moves on. Then a stress event arrives and the yield reveals its source: it was compensation for credit and liquidity risk that never showed up in calm markets and was never priced when the fund was chosen.

The lesson isn't to avoid MMFs — they're a genuinely good tool, and I've relied on them across most of the last eighteen years. The lesson is to remember what job they're doing. Preservation and liquidity are the mandate; yield is what you're allowed to keep once the mandate is met. Track it like the rest of treasury: the KPIs that measure treasury performance should reward safe, liquid, well-diversified cash, not the last few basis points squeezed out of it. Choose the fund that does the job, know what it holds, keep it inside the policy — and an MMF becomes exactly what it should be: a quiet, dependable home for cash, not a bet you didn't know you were making.

Part of the Cash & Liquidity Management guide. See also managing surplus cash and liquidity risk management. The newsletter sends one finance-systems pattern every two weeks.