How do I correct the sale of a second home which was entered in error as the sale of main home?

[Critter]

Delete the sale and start that section over ...  to enter this sale of a second home in TurboTax Online or Desktop, please follow these steps:

1. Once you are in your tax return, click on the “Federal Taxes” tab ("Personal" tab in TurboTax Home & Business)
2. Next click on “Wages & Income” ("Personal Income" in TurboTax Home & Business)
3. Next click on “I’ll choose what I work on” (jump to full list)
4. Scroll down the screen until to come to the section “Investment Income”
5. Choose “Stocks, Mutual Funds, Bonds, Other” and select “start’ (or “update” is you have already worked on this section)
6. The first screen will ask if you sold any investments during the current tax year (This includes any sale of real property held as an investment property so answer “yes” to this question)
7. Since you did not receive a 1099-B, answer “no” to the 1099-B question
8. Choose type of investment you sold - select Second Home

[dnaue]

Once I go thru the steps you advised, what do I need to send to the IRS since this would be an amended return for 2018?

[Critter]

Read the filing instructions that print with the amended return ... you send the 1040X plus any forms/schedules that changed.  In your situation that will be AT LEAST the Sch D & form 8949 but there may be others.