Live in NJ 100% but work in NY, how to find out the double-taxed income?

[Skyyy]

It has populated an amount already but it also asks me to enter the amount if different. How do I find out whether the amount is different and I should enter?

I have already done the NY state filing first and now I am doing the NJ state filing. 

[AmyC]

You can look at the NY return to see the taxable income and the tax liability. Follow these steps to locate your tax liability for NY.

1. Log into your return
2. Select state taxes
3. Enter the non-resident NY for which you need the liability
4. On the left, go to Tax Tools
5. Select Tools
6. Select View Tax Summary
7. You will see Summary of your NY Return at the top.
8. Locate the line that says Taxable Income
9. Locate the line that says Total Tax

Some states tax income the federal does not. For example: NJ taxes money you set aside in your retirement plan. Each state has different rules.