Refunds from foreign banks are only allowed on foreign withholding tax on amounts over 15%.
Therefore if the foreign bank is withholding 25%, it is only possible to claim back 10% from the foreign country.
Irish revenue allow a maximum foreign tax refund of 15%.
After this refund they apply the full 33% Irish withholding tax.
If the foreign bank withholds 25% and the Irish depositer does not reclaim the excess 10%, they will be liable to total withholding tax of 43%.
When foreign accounts are held in multiple foreign countries and some deduct no withholding tax while others deduct in excess of 15% a tax problem could be created.
By submitting the total deposit and interest paid on form 11, the calculated result will not necessarily be correct as a refund of in excess of 15% could be applied to some of the foreign banks interest.
This error could be discovered by Irish revenue when they receive details for each foreign account held by the Irish depositer.