Portfolio Clarity Foundations
Account Overlap
Definition
A state where the same holding or exposure appears in more than one account creating hidden concentration.
Why it matters
It inflates apparent diversification. What looks like multiple positions may be one economic exposure repeated.
What most investors miss
The gap between what the term means and how it is usually applied.
They diversify across brokers but buy the same ETF in each account. The broker view looks diversified. The consolidated view reveals the overlap.
How to read it
Check each position against the full consolidated view not just the account where it sits.
Multi-account lens
How this term reads differently across brokers and accounts.
When holdings span multiple brokers the same ticker can appear in each account. Without consolidation the overlap stays hidden.
Concrete example
What this looks like with real numbers.
Scenario
An investor holds iShares MSCI World in their ISA, Vanguard FTSE Developed World in their SIPP, and HSBC MSCI World in their GIA. Three funds, three brokers — but 93% underlying overlap. The portfolio is effectively a single-fund bet reported in three places.
What it reveals
Overlap is structural, not incidental. The investor designed diversification but executed concentration — visible only when holdings are mapped at the underlying level across all accounts.
Related terms
Terms that connect to account overlap.
ETF Overlap
The degree to which two or more ETFs in the portfolio hold the same underlying securities creating hidden concentration.
Hidden Concentration
A concentration risk that is invisible when accounts are reviewed separately but becomes clear at the consolidated portfolio level.
Fragmented Accounts
A portfolio state where holdings cash and records are split across multiple brokers banks wallets or spreadsheets.
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