Super basic question on state/local taxes

[fallstoclimb]

I'm working on my budget, trying to find a few more dollars to throw at charitable donations.

I live in MD, with a state income tax of 4.75% (plus $50), and a county tax of 2.83%.  I assume these are calculated separately so that my total state/local tax paid is 7.58%.

Here's my question:  Is that 7.58% of my W-2 income (total income minus our pretax retirement/health contributions) or is it 7.58% of my MAGI?  (W-2 income plus last year's state refund minus itemized deductions & personal exemptions).

For some reason I'm having trouble figuring this out with google. 

[johnny847]

Read the instructions for the MD tax forms.

Believe me, it's in there.

[fallstoclimb]

......you raise a very good point.

Can I just say that I haven't had enough coffee yet this morning??

[johnny847]

Haha I think this website botches the time zones for me but it does seem like it was early when you posted this!

Anyways, in general, states start with your federal AGI and make a few modifications.
But remember, that's AGI, NOT taxable income. This is important because charitable donations (along with other federal itemized deductions and exemptions) reduce your taxable income, NOT AGI.

Suppose MD does just use your federal AGI. Then MD would have to allow for charitable donations to be tax deductible for you to reduce your state (+ county) taxes with them.