How Do You Earn Interest on Uninvested Brokerage Cash?
Cash sitting in a brokerage account rarely just sits there doing nothing. Behind the scenes, it’s usually parked somewhere that pays at least some interest, even before an investor decides to buy anything.
The short answer
Uninvested cash in a brokerage account typically earns interest through an automatic “sweep,” where the balance is moved into a linked bank deposit account or a money market fund behind the scenes. The rate paid on that swept cash is set by the brokerage or its banking partner and can be noticeably lower than rates available elsewhere. Because of that gap, some investors choose to manually move idle cash into a separately purchased fund rather than leaving it in the default sweep.
How the default sweep works
When cash arrives in a brokerage account — from a deposit, a sold investment, or a dividend — it doesn’t just sit as a static number. Most brokerages automatically move it into a designated “sweep vehicle,” commonly either an interest-bearing bank account behind the scenes or a money market fund. This happens without any action from the account holder, and the cash remains available to withdraw or use for a new purchase at any time. The interest rate on the sweep is disclosed in the account’s fee schedule or a related disclosure document, and it can change over time as broader interest rate conditions shift.
Why the default rate can lag
The sweep option is built for convenience and liquidity, not necessarily for the highest possible yield. A brokerage may pay itself a spread by keeping the swept rate below what it earns on that same cash elsewhere, or below what a directly purchased money market fund yields. This isn’t unique to any one company — it’s a structural feature of how many default cash programs are built. The gap between a sweep rate and other available options can be small or fairly wide depending on the provider and the broader rate environment at the time, so comparing the actual numbers periodically is worthwhile.
It also helps to remember that the sweep exists to keep cash instantly usable, not to maximize what it earns. That trade-off makes sense for money that might be needed on short notice to cover a purchase or a bill, since the convenience has a value of its own even if the stated rate looks unremarkable next to other options.
Manually seeking a higher yield
- Buying a money market fund directly. Investors can often place a portion of cash into a specific money market fund rather than leaving it in the default sweep, similar to comparing a money market account against a high-yield savings account held outside the brokerage — the more deliberately chosen option often pays more.
- Watching settlement timing. Funds moved into a separately purchased vehicle usually take a business day or so to settle, so cash needed for an imminent trade may be better left in the sweep.
- Comparing across account types. The sweep rate inside a retirement account and a taxable account at the same brokerage isn’t always identical, so it’s worth checking each account separately.
- Reviewing periodically. Because sweep rates can move with broader interest rate trends, checking the current rate now and then avoids leaving cash on autopilot indefinitely.
A practical habit
Treating the default sweep as a starting point rather than a final answer is a reasonable habit for cash that isn’t needed immediately. Comparing the sweep’s disclosed rate against a directly purchased money market fund, and weighing the small settlement delay against the potential yield difference, helps put idle cash to more deliberate use rather than leaving it there simply by default. Checking the disclosure document once or twice a year, rather than assuming the terms never change, is enough to keep the comparison current without turning cash management into a constant chore.