Some countries require people to use a tax number when they are doing self-employed or freelance work, especially if the earnings exceed particular annual limits. Some countries do not. If you are an officially registered freelancer or self-employed, you will most likely know if you have one. If you are unsure whether you need one or not, we suggest that you speak to your local tax office or another official who can assist you in answering this question.
You will find a list of countries that use VAT numbers under the following link, along with their national specifications.
If you are a self-employed / freelancer and you have a tax number, then select "yes" and enter this number in the tax details section of your account. If your work does not require a tax number, you select “No” and simply leave the field blank. Make sure you click “Save” in both cases, even if you didn’t change any information.
The selection you make does not affect your payments.