As a california non resident, why do i owe additional california income taxes from my investment account?

[TerryA]

A typical investment account has only intangible assets such as CDs, stocks, mutual funds, etc., and as such the income from such accounts are taxable only by the state you live in. The Calif nonresident/part-year return, Form 540NR, computes your income and tax as if you were a resident the entire year so everything shows up in the beginning, but towards the end of the interview in Nonresident Adjustments is where you allocate the California-source income. In the interest, dividends, etc. fields you would enter 0 as the Calif-income.