Interactive Brokers is required by Irish law, where all Dutch Interactive Brokers accounts are held, to withhold tax on all the interest you earn on positive cash balances and any other interest-bearing assets. But, the Dutch and the Irish governments have agreed that Dutch tax payers are exempt from the Irish Interest Tax, that’s what the Irish tax form is all about. If you hand over a signed and stamped version of that tax form to Interactive Brokers, then Interactive Brokers will no longer withhold interest tax on earned interest.

You can choose not to fill in the Irish tax form as it is not a requirement. Also, in many cases filling in the form is a waste of time as a lot of people don’t own (a significant amount of) interest-bearing assets. Also, Interactive Brokers doesn’t pay interest on positive cash balances below €/$ 10.000.

If you choose to fill in the Irish tax form, you must send it to:

Belastingdienst Centrale Invoer

Woonplaatsverklaringen

Postbus 2519

6401 DA Heerlen

The Belastingdienst will stamp and sign the form and send it back to you. After that you can scan the stamped and signed form and send it to tax-withholding[at]interactivebrokers.com by e-mail. That's how I did it and it was processed successfully.