More than half of the postdocs at UC Berkeley are from another country and thus require a visa to come to the US. Most likely, your host department will arrange for the proper visa in your situation, but there are always questions arising as to the details of the specific visas for entry to the US and travel afterwards.
You can find the latest information on Visa policies and instructions at the Berkeley International Office.
The International Office also provides workshops on visa renewal, changing of visa status and other visa-related issues, and you should get information on those by email from the VSPA (Visiting Scholar and Postdoc Affairs).
Some of you might also be eligible to participate in the yearly Green-Card Lottery.
For any other visa-related questions, contact the International Office
Every postdoc has to pay taxes, whether you are paid by US government agency, University or by your own country! The deadline to submit your tax report (better known as a tax return) is on April 15.
You need to pay two types of tax: federal and state tax. The amount you need to pay depends on your postdoc category, your marital status, pertinent tax treaty between US and your home country, etc. Also, federal and state taxes have different rules so…well, you get the picture – it’s complicated.
IMPORTANT: Foreign nationals who receive income are required to complete a Glacier record. Glacier is a tax compliance program which determines your tax residency status, withholding tax rates, and tax treaty eligibility, etc. Glacier will also upload tax forms (1042-S tax form) at year end which is available around March the following calendar year. In order to create a Glacier record, your Home Department must submit a "Glacier Information Form" on your behalf to email@example.com. Once you are complete, please submit all your Glacier documents to the Central Payroll office at 2195 Hearst Ave, Ground Floor Room 120 or email them to firstname.lastname@example.org. For any Glacier related questions, please email email@example.com.
If you are an international postdoc, feel free to contact the Berkeley International Office is a great resource to learn more about the subject (http://internationaloffice.berkeley.edu/tax_assistance) and they offer great seminars where they show in details how to fill in the forms. Also, you are entitled to use a web based program called CINTAX (Complete International Tax Preparation) which makes filling the tax return easy.
Links for further reading:
Internal Revenue Service - http://www.irs.gov/
California Franchise Tax Board - http://www.ftb.ca.gov/