Hi, Is sales tax deduction over the standard deduction limit (12K) for individuals? Ex, i paid sale tax of $900 for car. So, is deduction 12900 or 900 only?

You do that by actually entering your information yourself and letting the software do the calculations.  You do not ask the public user forum to do your tax return for you.

sorry! i am not clear with itemised deduction and standard deduction, so rephrased the question. Hope its clear now!

No you do not add to the Standard Deduction.  It is either your Itemized Deductions or the Standard Deduction, whichever is more.

Do you think you will have enough to itemize this year?  This year the Standard Deduction will be doubling so many people will be switching to the Standard Deduction.  And there is a max 10,000 limit (5,000 MFS) of property tax and state taxes "SALT".

FAQ on 2018 changes https://ttlc.intuit.com/questions/4482394-how-will-tax-reform-affect-my-2018-federal-tax-return

For 2018 the standard deduction amounts are:
Single 12,000 + 1,600 for 65 and over or blind
HOH 18,000 + 1,600 for 65 and over or blind
Joint 24,000+ 1,300 for each 65 and over or blind
Married filing Separate 12,000 + 1,300 for 65 and over or blind

If you itemize your deductions you can either take the state and local SALES TAX deduction OR the state and local INCOME TAX deduction whichever is greater. There are a couple items like car sales tax you can add to the general sales tax table.  That is mainly for people who live in a state without a state income tax.

thanks!