The USA tax authority (IRS) requires that all International (Non- USA) creators complete a W8-BEN form to certify that all of their income was earned outside the USA.
Creators will find a secure electronic version of this form from their payment settings page after selecting I am a non-USA person or corporation (International) that they'll need to fill out before receiving payment on Patreon.

Once you have completed it, it will show you the date that you submitted your form.

How to complete a W-8BEN form?
Patreon is not a registered tax professional, so I can't provide you with advice on how to fill out this form. However, you can find the IRS instructions for how to fill out the W-8BEN here: https://www.irs.gov/instructions/iw8ben/ch02.html
Here are the instructions for the specific lines:
Line 8. If you are providing this Form W-8BEN to document yourself with respect to a financial account that you hold with a U.S. office of a financial institution, provide your date of birth. Use the following format to input your information MM-DD-YYYY. For example, if you were born on April 15, 1956, you would enter 04-15-1956.
Part II
Line 9. If you are claiming treaty benefits as a resident of a foreign country with which the United States has an income tax treaty for payments subject to withholding under chapter 3, identify the country where you claim to be a resident for income tax treaty purposes. For treaty purposes, a person is a resident of a treaty country if the person is a resident of that country under the terms of the treaty. A list of U.S. tax treaties is available at http://www.irs.gov/Individuals/International-Taxpayers/Tax-Treaties.
Note: Again, Patreon is not a registered tax professional. For any questions regarding taxes, please consult your local tax professionals.