I am trying to extract the data of all my customers My problem is that I can't get the field "Tax Reg. No." that I define in the "Tax Information" tab in the client form.

Thanks for checking out the Community space, userjavier-lis.

I've checked your earlier post and found out that you've posted the same question twice. 

Please know that the duplicate one was already answered by my colleague, MaryLurleenM. Also, she used a multilingual translation service to answer your question since it was written in Spanish. You can read her response through this link: https://quickbooks.intuit.com/learn-support/global/tax/re-datos-de-cliente/01/730861#M889.

I've also attached some articles that help your customers in QuickBooks Online:

• Edit customer information
• Import customer contact information

Keep me posted if you have any other concerns or questions. Have a pleasant day ahead.