Is Corporation LLC Tax ID Same As Federal Tax ID number? 

   The corporation tax federal ID number assigned to you when you incorporate a business that is the federal tax  ID number.   The state assigns you a state corporation number.    The employer's federal tax id number is the number you apply for after you incorporate through the IRS and it is the on equivelant to the federal tax ID number for your corporation ID.    It serves both as a corporation ID and a employer ID if  the employers federal tax id number is how IRS knows who you are. the corporate number is how the state knows who you are

   Can I use a corporation ID number for all my businesses under that corporation? I have a corp already with reseller permit and business license, that is, ABC Copr. If I want to run the business under a different name, that is, "Xyz" Do I need just to apply the dba certificate? Or do I need to apply reseller permit or business license for the Xyz?  

d: 000 Your business information renders the following legally required documents: 1. A Business License, 2. A Sellers Permit, 3. A Federal Tax ID Number, 4. A State Employer Identification Number, and 5. A DBA or instead of a DBA you can incorporate or form an LLC. Thus alternatively, you can form an LLC limited liability company or Incorporate your business and then you will not need a DBA Business Assumed Fictitious Business Name Certificate because there will not be an assumed business name involved. In fact, namely, the LLC or corporation name is not a fictitious name because it is the legal name of the legal person that the corporation becomes subsequently to its legal recording of the business document.
Additionally, If you eventually decide to employ workers, as mentioned above, you will also need a federal employer number EIN and a state EIN.

You will have to check on the requirements of your state. For example, if you live in CA, contact  Our Corporations Division- Telephone: (310) 455 6675

A federal corporation  ID number or a State Corporation ID Number can be obtained here online.

Example:
"All corporations must get both an IRS / Federal employer identification number (EIN) and a State Employment Development Department employer account number. Both of these taxpayer numbers (IRS employer number and  employer number) should be obtained AFTER the date of incorporation."
 

As of 2/19/2010 the price is $39.00 but can change at any time.