I buy and sell US stocks using an off shore stock broker.
The off shore broker does not report to the IRS and does not supply clients with form 1099-B
How to report income, from day trading stocks, using an off shore stock broker?
The Old Guy
The taxpayer is responsible for filing their own taxes accurately not their brokerage firms. In North America broker/dealers assist their clients by providing information needed to file an accurate tax form.
Like all reported activity it is the responsibility of the tax payer so it is in their best interest to maintain their own records - that' why there are spread sheets.
A Hunch
Calculate the information, just like you would to verify your 1099-B is accurate.