Does TT Premier have Schedule D and form 8949 to report additions to cost basis of a mobile home (second home) that I sold? Will the IRS accept my spreadsheet instead?

TurboTax Online Premier supports IRS Schedule D and IRS form 8949.  To report the sale of a second home, follow these steps:

• Click on Federal down the left side of the screen.
• Click on Wages & Income down the left side of the screen.
• Scroll down to Investments and Savings and click the down arrow to the right.
• Click Start / Revisit to the right of Stocks, Cryptocurrency, Mutual Funds, Bonds, Other.
• At the screen Let's finish pulling in your investment income, select Add investments.
• At the screen Let’s import your tax info, click Enter a different way.
• At the screen OK, let’s start with one investment type, click Other, land, second home, personal items, 1099-S).  Click Continue.
• At the screen Now, enter one sale, use Second home as What type of investment.
• Enter sale information.  Select Continue.

Do you mean that your spreadsheet explains your cost basis of the second home?  Does it include original cost information as well as the cost of improvements and additions?

Do not submit your spreadsheet but, certainly, retain your work should you have to justify the cost basis that you report to a tax authority at a later time.