How do I enter sales of personal property on Mercari and Paypal if I did not receive a 1099-K form from either? I made $4689.

Sale of personal items may be reported on Schedule D IRS form 1040 and Schedule 8949.

Personal items sold for less than their cost basis report $0 capital gain on line 7 of the Federal 1040 tax return.

Personal items sold for more than their cost basis report the gain on line 7 of the Federal 1040 tax return.  See this example.

                                              Selling                   Cost

                                              Price                      Basis

Item 1                                   $500                       $2,000                 Capital loss on personal item = $0 loss

Item 2                                   $400                       $300                    Capital gain on personal item = $100 gain

Item 3                                   $100                       $100                    No capital gain or loss

                                              $1,000                   $2,400

In TurboTax Online, to report such a sale of personal items, follow these directions.

• Down the left side of the screen, click Federal.
• Down the left side of the screen, click Wages & Income.
• Click to the right of Investments and Savings.
• Click to the right of Stocks, Cryptocurrency, Mutual Funds, Bonds, Other.
• Click Add investments.
• At the screen Let's import your tax info, select enter a different way.
• At the screen OK, let's start with one investment type, select Other, Land, Second homes, Personal items.
• Select Add another sale to report additional transactions.

See also this TurboTax Help.