Give Well seems to not be able to help in Netherlands with Tax-deductible transactions, but work with the help of Effective Altruism Foundation which is a non-profit that claims tax-deductible transactions for many countries, including Netherlands, Germany and switzerland.

German, Swiss, and Dutch donors can make a tax-deductible donation to the Effective Altruism Foundation for the support of GiveWell or one or more of our recommended charities.

Once we click the donate page, we have options for visa, direct debit, and bank transfer. Went through the bank transfer with a fake address, to see the process, but I guess the system thought I made the donation. Need to clarify it I guess.

EAF will send our information to GiveWell.

Tax-deductible

In Germany, Switzerland (see confirmation of tax exemption and deductibility list (Spendenliste)) and the Netherlands EAF itself is directly exempt from taxes.
-EAF FAQ #5

EAF will send the tax forms in the month of january.

This website, claims that as long as an institution is registered in the ANBI database, then it is tax-deductible. Checked the ANBI database. Both MIRI and EAF are in the ANBI

And Also:

Your donations are deductible if the total amount is at least 1% of your income. The maximum amount is 10% of your income. If you have a partner then both incomes are taken together.

Need to verify the above

Things to check with Belastidienst!