If any unamortized start-up costs or organization costs remain on your books when your business is closed, deduct the balance remaining on your final return.

For example, if you elected you amortize organization costs over five years, and you still have two years of unamortized organized costs remaining when your business is closed, deduct the remaining two-year balance on your final return.

You can add them as Business Expenses. Continue past the expense categories (or choose Other Miscellaneous Expenses) to the page titled "Enter Business Expenses Not Yet Reported" and enter the description & amount.