What Is a Money Market Fund? A Comprehensive Guide to Short-Term Cash Management

TL;DR: A money market fund (Money Market Fund) is a fund that invests in short-term, highly liquid debt instruments and is commonly used for short-term cash management. Its key features include relatively high liquidity, daily interest accrual, and a low entry threshold. However, it also involves risks such as interest rate, credit, and liquidity risk—so it is not risk-free—and it is not protected by Hong Kong’s Deposit Protection Scheme. Some investors use it to park idle funds, or to temporarily hold cash while waiting for investment opportunities.

In an environment where bank interest rates fluctuate repeatedly, many Hong Kong investors have started looking for wealth management tools that keep funds flexible while also putting idle assets to work. Money market funds (Money Market Fund, or MMF) have gained attention in this context. Their price volatility is generally lower than that of stocks, and unlike time deposits they do not require funds to be locked up—but neither returns nor principal are guaranteed. This article explains how money market funds work, what they hold, key risk considerations, and how to assess whether they fit your financial plan.

Definition and how money market funds work

A money market fund is a collective investment scheme in which a fund manager pools money from multiple investors and invests it in a range of short-term money market instruments with high credit ratings. The fund generally aims to minimize fluctuations in principal and deliver returns close to short-term market interest rates, but neither returns nor principal are guaranteed.

Main investment asset classes

Under the Securities and Futures Commission (SFC) of Hong Kong’s Code on Unit Trusts and Mutual Funds, a money market fund’s portfolio must meet stringent liquidity and credit rating requirements. Its main investments include:

• Short-term government bonds: short-term notes issued by governments; generally highly rated, but still not entirely risk-free
• Certificates of Deposit (Certificates of Deposit): time-deposit certificates issued by banks with a fixed interest rate and maturity date
• Commercial paper (Commercial Paper): short-term unsecured debt instruments issued by higher-rated companies
• Repurchase agreements (Repurchase Agreements): short-term borrowing arrangements collateralized by bonds, with an agreement to repurchase at maturity

To control interest rate risk, under the SFC’s Code on Unit Trusts and Mutual Funds, the portfolio’s weighted average maturity must not exceed 60 days, reducing the extent to which assets are exposed to interest rate fluctuations over a prolonged period.

Daily interest accrual mechanism

Money market funds generally accrue interest daily. Interest is calculated on a day-by-day basis and reflected in the fund’s net asset value (Net Asset Value, NAV). Investors do not need to wait for fixed distribution dates—each day of holding accumulates returns—which is also one reason they can be more attractive than bank demand deposits.

The three core features of money market funds

1. High liquidity

Most money market funds support T+0 or T+1 redemptions, meaning you can withdraw funds the same day or the next business day, without being subject to a fixed lock-up period. For investors who need to allocate cash at any time, this flexibility is especially important. For example, if an investor is waiting for a suitable entry point in the stock market, they can first place idle funds into a money market fund to accrue interest daily; once an opportunity appears, they can redeem immediately and switch into other assets.

2. Relatively stable returns

Money market fund returns mainly reflect short-term market interest rates and will change with the rate environment. When short-term rates rise, money market fund yields typically rise as well; when rates fall, yields also decline (actual returns vary by fund, and past performance does not represent future results).

3. Low entry threshold

On some platforms, the minimum subscription amount for a money market fund can be as low as a few dozen Hong Kong dollars, allowing ordinary retail investors to participate. In addition, most money market funds have waived subscription and redemption fees, and the main cost to investors is the fund’s management fee (Expense Ratio). When choosing products, it is recommended to prioritize options with lower management fees to reduce the impact of costs on overall returns.

Tip: When choosing a money market fund, pay attention to the fund’s “expense ratio” (Expense Ratio). Net annualized yield = underlying asset yield − management fee − other expenses. The lower the management fee, the more an investor typically takes home.

Key differences between money market funds and time deposits

When considering short-term cash management, many Hong Kong investors compare money market funds with time deposits. Each has different characteristics, and investors should decide based on their own needs.

Differences in deposit protection

Time deposits are bank deposits and are covered by the protection scheme administered by the Hong Kong Deposit Protection Board, with protection of up to HKD 500,000 per depositor. Money market funds, by contrast, are investment products and are not covered by the Deposit Protection Scheme. This is a fundamental difference between the two, and investors should fully understand it when allocating funds.

Differences in flexibility and lock-up periods

Time deposits typically require funds to be locked up for a period of time (commonly one month to one year). Early withdrawal may result in losing part or all of the interest. Money market funds have no mandatory lock-up period; investors can redeem flexibly as needed, making them suitable for scenarios that require higher liquidity.

Differences in interest rate sensitivity

A time deposit’s interest rate is fixed at the time of deposit and is not affected by changes in market interest rates during the deposit term. Money market fund returns, however, adjust with changes in short-term market rates; when rates fall, fund returns may decline accordingly.

Key risks of money market funds

Although money market funds are widely regarded as lower-volatility investment tools, investors must clearly understand their potential risks and avoid misunderstanding them as “zero-risk” products.

Interest rate risk

When market interest rates rise, the value of existing bonds and notes held by a money market fund will decline relatively, which may temporarily affect the fund’s NAV. Conversely, when interest rates fall, fund returns will also decrease. During the U.S. Federal Reserve’s sharp rate hikes in 2022, prices of some money market instruments experienced volatility, showing that the interest rate environment can influence fund performance to some extent.

Credit risk

Commercial paper and certificates of deposit held by money market funds involve the credit risk of the issuing institutions. If an issuer encounters financial difficulties, the related assets may incur losses. Historically, in 2008 the Reserve Primary Fund in the U.S. held Lehman Brothers commercial paper; after Lehman’s bankruptcy, the fund’s NAV fell below USD 1, becoming a cautionary case for the industry.

Liquidity risk

Under extreme market stress, if a large number of investors redeem at the same time, the fund may need to sell assets at lower prices to meet redemption demand. The SFC therefore requires money market funds to maintain at least 7.5% of NAV in daily liquid assets to enhance resilience.

Note: Money market funds are not bank deposits and are not protected by Hong Kong’s Deposit Protection Scheme. Before investing, please read the fund’s offering documents carefully to understand the relevant risks and fees.

Exchange rate risk

If an investor chooses a foreign-currency-denominated money market fund (such as USD), exchange rate fluctuations may affect the actual return once converted back to Hong Kong dollars. While a USD money market fund’s returns may be relatively stable in USD terms, unfavorable movements in the USD/HKD exchange rate may affect the converted return.

Who should consider money market funds?

Money market funds are not suitable for every investor or every situation. The following scenarios are for reference:

Parking short-term idle cash: If you have a sum of money that you will not use in the short term (for example, one to three months) and you do not want it to be affected by large market swings, a money market fund can be a temporary parking option, allowing the funds to keep accruing interest while you wait.

A cash buffer within a portfolio: Some investors keep a certain proportion of cash or cash equivalents in their overall portfolio as liquid funds to respond to market opportunities or unexpected needs. A money market fund can play the role of a “cash substitute,” maintaining high liquidity while offering more competitive returns than demand deposits.

A transitional arrangement while waiting for investment opportunities: If you have just completed an asset sale (for example, selling stocks) and are waiting for a suitable time to re-enter the market, you may consider temporarily allocating the funds to a money market fund, rather than leaving them idle in a zero-interest account.

Money market funds are not suitable as a primary tool for long-term asset appreciation; their returns are typically lower than growth assets such as stocks and real estate. Their main function is capital preservation and short-term management. For more comprehensive knowledge about fund investing, please refer to A Beginner’s Guide to Fund Investing.

Money market funds under Hong Kong’s regulatory framework

Under the SFC’s requirements, money market funds offered to the public in Hong Kong must comply with specific requirements for money market funds under the Code on Unit Trusts and Mutual Funds, including:

• The portfolio’s weighted average maturity (Weighted Average Maturity) does not exceed 60 days
• At least 7.5% of NAV must be held in daily liquid assets
• Investments are limited to short-term instruments with high credit ratings
• A liquidity risk management framework must be established, with regular stress testing

According to the SFC and the Hong Kong Monetary Authority (HKMA)’s Joint Product Survey for 2022, money market funds were the best-selling collective investment scheme products that year, with their share of total turnover among the five major CIS categories rising sharply from 33% in 2021 to 61% (source: Hong Kong Monetary Authority). This reflects continued growth in demand for money market funds among Hong Kong investors.

How to invest in money market funds in Hong Kong

Hong Kong investors can invest in money market funds through multiple channels:

Traditional banks: Large commercial banks (such as HSBC and Hang Seng) offer their own branded money market funds, which can be subscribed to via online banking or at branches.

Fund companies: International asset management companies such as J.P. Morgan and Morgan Stanley offer HKD- and USD-denominated money market funds, which can be subscribed to directly through their platforms.

Brokerage platforms: Some online brokerage platforms offer money market funds as cash management tools, allowing investors to use funds flexibly while waiting to enter the market. Longbridge Securities offers a range of investment products, where investors can learn about the available investment choices on the platform.

Factors to consider when choosing products:

• Fund dealing currency (HKD, USD, or other foreign currencies)
• The level of the expense ratio (management fee)
• Fund size and history (larger funds usually have stronger liquidity)
• Fund ratings (some money market funds are rated AAAmmf by agencies such as Fitch)
• The convenience of the subscription and redemption process

Frequently asked questions

Are money market fund returns guaranteed?

Money market fund returns are not guaranteed. Fund returns fluctuate with changes in short-term market interest rates and are not protected by the Deposit Protection Scheme. Past performance does not represent future results, and investors should make decisions with this understanding.

How long does it take to redeem a money market fund?

Redemption times vary by fund, typically ranging from T+0 (same day) to T+1 (next business day). The specific processing time depends on the fund’s rules and the time the redemption instruction is submitted.

Are money market funds suitable as an emergency reserve?

Because of their high liquidity, some investors consider money market funds for short-term emergency reserve management. However, since redemption proceeds typically take one to two business days to be credited, and because they are not protected by deposit protection, investors should fully assess their liquidity needs and risk tolerance before deciding.

Which is more suitable: HKD or USD money market funds?

This depends on your intended use and how you view exchange rate risk. If the funds are mainly for HKD expenses, choosing an HKD-denominated fund can avoid the impact of exchange rate conversion; if you have USD needs (for example, planning to invest in U.S. stocks), a USD-denominated fund may be more flexible. However, note that exchange rate fluctuations for USD funds may affect the actual return when converted back to HKD.

What is the difference between money market funds and MPF Conservative Funds?

MPF Conservative Funds are structurally similar to money market funds in that they also invest in short-term money market instruments, but they are regulated under different frameworks. MPF Conservative Funds are regulated under the Mandatory Provident Fund Schemes Ordinance and have specific fee caps, while general money market funds are regulated under the Code on Unit Trusts and Mutual Funds. In addition, MPF contributions are subject to statutory restrictions, and liquidity is not as flexible as that of general money market funds.

Summary

A money market fund invests in short-term money market instruments with high credit ratings. Its core advantages are high liquidity, relatively stable returns, and a low entry threshold. It is suitable as a short-term parking tool for idle funds, or as a cash buffer allocation within a portfolio, allowing funds to keep accruing interest while waiting for market entry opportunities.

However, investors should also clearly understand the risks: money market funds are not risk-free; they remain somewhat vulnerable to interest rate changes, credit events, and liquidity stress, and they are not protected by Hong Kong’s Deposit Protection Scheme. Before making any investment decision, it is recommended that you fully understand the product’s operating mechanism, fee structure, and potential risks.

Which tool to choose depends on your investment objectives, risk tolerance, market views, and experience level. No matter which investment tool you choose, you must fully understand how it works, its risk characteristics, and its trading rules, and establish a sound risk management plan. You can learn more investment knowledge via Longbridge Academy or Download the Longbridge App.