Can I receive a refund of non-resident Canadian taxes that were withheld in the previous tax year?

Overview:

Non-US persons or entities must file an income tax return with the United States tax authority in order to claim a refund of over withheld or overpaid tax…

Your tax form has either expired or the information was not correct and as a result there was back up withholding tax.  Once you update or correct your tax form and if it is done in the same calendar year then IBKR can refund the tax directly to your account…

In general, amounts withheld for US taxes are non-refundable. However, under certain circumstances, such as an incorrect rate being applied to withhold tax, a refund can be obtained. If you are an individual, file either Form 1040NR, "US Nonresident Alien Income Tax Return" or 1040NR-EZ "U.S. Income Tax Return for Certain Non-Resident Aliens with No Dependents" to obtain a refund. There are similar US forms for trusts and corporations. IRS Publication 515 "Withholding of Tax on Non-Resident Aliens and Foreign Entities" and IRS Publication 519, "US Tax Guide for Aliens", available free at …

RSPs do not generate tax forms related to annual investment earnings. However, forms are issued for contributions and withdrawals.

A withdrawal of funds from an RSP constitutes a de-registration of the plan and is subject to withholding tax. The tax will be withheld by IBKR at the time of the withdrawal. The gross amount of the RSP withdrawal will be included in the T4RSP slip, and will be counted towards the general income that one receives for the calendar year…