Multi-Account Tracking & Data Quality
FX Mismatch
Definition
A distortion in portfolio value or return that occurs when different accounts or tools use different exchange rates or valuation dates.
FX mismatch occurs when transaction currency, asset currency, base currency, or valuation rate are handled inconsistently across records or tools.
Why it matters
It creates phantom gains and losses that do not reflect real economic change. Two brokers valuing the same holding in different currencies on the same day may show different numbers.
What most investors miss
The gap between what the term means and how it is usually applied.
They add portfolio values from different brokers without checking whether the same FX rate was used. The total is mathematically wrong even if each individual number is correct.
How to read it
Fix a portfolio currency and a valuation date convention. Then convert all accounts to that currency using the same rate before combining values.
Multi-account lens
How this term reads differently across brokers and accounts.
FX mismatch is almost guaranteed in multi-currency multi-broker portfolios unless a consistent conversion methodology is enforced across all accounts.
Related terms
Terms that connect to fx mismatch.
Portfolio Currency
The base currency used to express total portfolio value when holdings are denominated in multiple currencies.
Reporting Currency
The currency in which the portfolio's gains losses and income are reported for tax purposes.
Currency Exposure
The portion of the portfolio whose value changes when exchange rates move even if no currency conversion has taken place.
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