If you are under the New Jersey filing threshold, Lines 30 through 49 of your New Jersey Form NJ-1040 should not be completed.
Per the New Jersey Instructions for the NJ-1040 New Jersey Resident Return, page 19:
Subtract Line 28c from Line 27 and enter the result. If zero or less, make no entry.
You are not required to file a return if your income is at or below the filing threshold. However, you still need to file if you:
Do not complete lines 30 through 49. Continue completing the return with line 50.
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