The existing answers to this question are unclear and potentially misleading.
Capital gains for single-member LLCs operating as disregarded entities go on the owner's Schedule D. You do not want to enter LLC cap gains as regular business income.
From https://finance.zacks.com/capital-gains-offsets-llc-operating-losses-7938.html:
Unless a single-member LLC makes the election to be taxed as a corporation, the IRS will consider the LLC a “disregarded entity.” A disregarded entity is not recognized as being separate from the owner for taxation purposes. In this case, the LLC’s capital gains and losses are treated as though directly incurred by the individual. The capital gains and losses are reported on Schedule D along with any other capital gains and losses. Net LLC capital gains tax is determined at the individual taxpayer’s rate. Net losses are deductible up to the IRS limits.
