You handle this by modeling the account as a ledger with immutable entries containing unique identifiers rather than a single mutable balance. The ledger entrie

You handle this by modeling the account as a ledger with immutable entries containing unique identifiers rather than a single mutable balance. The ledger entries are facts. The balance is a derived computation. Only store facts, not derived computations. (At some point for efficiency reasons you might need to prune the transactions, but this often involves trade-offs like not allowing any new "lost" transactions older than date X.)