Yes, eHerkenning EH3 is suitable for filing your dividend tax return. You can apply for a EH3 eHerkenning, but the Limited Belastingdienst EH3 is also suitable for this purpose.
If you already have an EH3 eHerkenning without the authorization for Dividend tax return, you can add an additional authorization to your eHerkenning by logging in to My Reconi.
If you already have the Limited Belastingdienst EH3, you do not need to add anything to your eHerkenning. You will automatically have access and be able to log in to the Tax Authorities Business for your Dividend tax return.