I received a lump sum payment from Social Security for tax year 2017. I entered in the amount and the amount from line B. I have rechecked all of the entries. I get this message: "Earlier year taxable social security for taxpayer should not be more than $xxxxx, 85% of the sum of line B.
Yes, that's the correct error message you get when you enter more than you should.
There's an option to enter a lump-sum payment. The reason it's entered separately is because the taxable amount for each year needs to be figured. Make sure you have that year's adjusted gross income to correctly compute.
I'm not exactly sure how to get there in Mac, but you'll find it as a separate category in your Retirement & Social Security section under Income.