@marky19628434 , please tell more of the scenario -- details such as country, type of income and obviously the article of the treaty you are asserting. Also what is your own immigration / tax status i.e. are you a US person ? Where is your tax home ?
Assuming that you are probably talking about treaty based limitation of tax rate for some specific types/categories of passive incomes ( like interest, dividend etc. ), then it would be nice to know the gross foreign income for that category -- the limitation is usually complied by a mechanism of adjusting the gross amount to be taxed by the US.
Please answer my questions . Will circle back once I hear from you .