Commission payment to non resident foreign national taxable?

TDS will be deducted sec 195

if pan not provided , deduction percentage would be the highest @ 20 %

If the person is an Indian, the person would have paid tax over and above TDS on his income (commission in this case). Now how the income tax department is going to get the remaining tax from the foreign national? Obviously it can not get. Does it mean just paying TDS by the payer is good enough for the income tax department or whether the payer should pay the complete tax that would be more than TDS?