When filing the state income tax form which form do you file is it the 1040 a or 1040 schedule a or both?

You file whatever the state tax instructions tell you to file, which may be neither of those things. ("Both" is clearly wrong, for reasons that will be explained later.)

The IRS has three main income tax forms. The instructions for each form contain a short worksheet telling you whether you can use it or not.

  • 1040 is the "standard" income tax form. Nearly anyone can use this form (along with various schedules) to file their return. It's the most complicated of the three.
  • 1040A is a shorter, simplified form. Most people who do not itemize deductions can use this form.
  • 1040EZ is a very short and greatly simplified form for people with no dependents (other than, possibly, a spouse) whose income is almost entirely from wages, salaries, or tips, with less than $1500 of taxable interest income. Like the 1040A, the 1040EZ does not allow itemized deductions (and simplifies things further by combining personal exemptions with the standard deduction).

In addition, there's also a Form 1040 Schedule A, which is used to list itemized deductions. It can only be used with Form 1040, because neither Form 1040A nor Form 1040EZ allow itemized deductions.

Most states require that you file a copy of your federal return along with your state return. Filing a copy of both Form 1040A and Form 1040 Schedule A would be incorrect, as this is not a valid combination ... you need either 1040 plus 1040 Schedule A (and any other schedules you sent to the feds), or 1040A pretty much by itself or 1040EZ also pretty much by itself. Along with your state return, which generally has to "match" the federal return ... if you used federal 1040, in California you have to file state form 540, if you used federal 1040A you have to file state form 540A, and if you filed federal 1040EZ then you need to use state form 540EZ.