North Carolina does not have a state itemizable deduction for federal investment interest expense from Schedule A. Looking at D-400 Schedule A for North Carolina itemized deductions, it appears N.C. only permits these specific line items in the itemized deductions total:
5. Home Mortgage Interest and Real Estate Property Taxes After Limitation
6. Charitable Contributions (See instructions)
7. d. Medical and Dental Expenses After Limitation
8. Repayment of Claim of Right Income