Hello Patricia de los Santos Milán,
Thank you for posting in Microsoft Community forum.
I'm sorry, but as a Microsoft customer support agent, I am not authorized to provide tax-related documents such as a W9 form. However, you can visit the Microsoft website and navigate to the "Contact Us" page to get in touch with the appropriate department who can assist you with your request. Alternatively, you can contact Microsoft's customer support directly for further assistance.
In addition, I found some information, but I don't know if it still works, so I'll provide it to you as a reference.
Maybe you can obtain a W9 form from Microsoft by contacting their Accounts Payable department. You can reach them by phone at 1-800-936-4900 or by email at msinvoice@microsoft.com.
Alternatively, you can also download a W9 form directly from the IRS website at https://www.irs.gov/forms-pubs/about-form-w-9. Once you have the form, you can fill it out with the necessary information and provide it to Microsoft.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Haijian Shan