How to get a copy of a SSA-1099
https://faq.ssa.gov/en-us/Topic/article/KA-01723
You can get a replacement SSA-1099 from Social Security
https://www.ssa.gov/myaccount/replacement-SSA-1099.html
ENTER SS
Enter a SSA-1099, SSA-1099-SM or RRB-1099 under
Federal Taxes on the left side or top
Wages and Income
Then scroll down to Retirement Plans and Social Security
Then the second line - Social Security (SSA-1099. RRB-1099) - click the Start or Revisit button
2020 1040 line 6a is the gross Social Security amount and 6b is the taxable part of Social Security.
Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0