Portfolio Clarity Foundations
Idle Cash
Definition
Cash sitting in a brokerage or wallet account that is not invested and not earning meaningful return.
Why it matters
It is a drag on real portfolio return that is easy to miss when accounts are reviewed separately.
What most investors miss
The gap between what the term means and how it is usually applied.
They do not count idle cash as part of the portfolio. It is. And if it is spread across accounts the total drag is invisible until it is consolidated.
How to read it
Read it as a position not as a neutral state. Idle cash has an opportunity cost that compounds over time.
Multi-account lens
How this term reads differently across brokers and accounts.
When cash is spread across multiple broker accounts the total idle position is invisible unless all accounts are consolidated.
Concrete example
What this looks like with real numbers.
Scenario
Across three broker accounts, an investor holds £9,200 / €4,100 / $6,400 uninvested. At a conservative 6% expected portfolio return, approximately £19,700 in idle cash costs roughly £1,180 per year in unrealised opportunity — before considering FX effects.
What it reveals
Idle cash is easy to undercount when spread across brokers and currencies. No single account makes it obvious that 12–18% of total capital is sitting idle.
Related terms
Terms that connect to idle cash.
Cash Drag
The performance reduction caused by holding uninvested cash that earns less than the portfolio's investment return.
Cash Position
The total amount of uninvested cash held across all accounts in the portfolio.
Investable Capital
The portion of total wealth that is liquid and available for investment decisions right now.
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