Per the IRS website
"The annual tax return for a partnership, corporation, S corporation, limited liability company or trust includes check boxes near the top front page just below the entity information. For the tax year in which your business ceases to exist, check the box that indicates this tax return is a final return. If there are Schedule K-1s, repeat the same procedure on the Schedule K-1."
No mention of Schedule C sole proprietorship.
I asked TaxACT customer support for their advice, they never mentioned anything about a special notation on Schedule C.
