While there is no transaction limit enforced by IB, TurboTax restricts the import to files containing no more than between 2,000 to 2,500 transactions for system performance purposes. Note that the precise limit depends upon the volume of data in each transaction, which explains why TurboTax cannot provide an exact number. In the event the import of a file containing transactions above the threshold is attempted, an error message will appear (e.g., “The selected file contains no importable tax information. Please select a different file”).
IB is not aware of any workaround for this restriction and suggest that you contact TurboTax Support for assistance.