North Carolina Administrative Code Title 17 — Revenue
17 NCAC 05C .1403 — Taxable Bonds
A portion of the premium paid upon the purchase of a taxable bond may be deducted in the taxable year only if an adjustment is made to the basis of the bond. If a taxpayer elects to amortize the premium, the basis for determining gain or loss will always be original cost less the amount of premium amortized and deducted in its tax returns through the year of disposal. Otherwise, the basis of a taxable bond for determining gain or loss will always be the entire amount paid for the bond.
Source: official text