The IRS does random compliance checks. It doesn’t necessarily mean that there is something wrong with your return.
The IRS can, and does periodically, request documentation for amounts reported on your tax return; see below for some of their new initiatives. The Social Security Administration (SSA) send out Forms SSA-1099 and RRB-1099s. The 1099-R section is for pensions, IRAs, 401ks, etc. (non social-security retirement). Check your Form 1040 and see what amounts are reported on Lines 4-6, as you may need to amend your return. Social Security is taxed differently than other types of retirement income.
You can upload documents in response to an IRS notice, phone conversation or in-person visit. Don’t use this tool to file a tax return.
IRS Doc Upload Tool
To upload your documents and verify your identity, you’ll need to enter:
Understanding your IRS notice or letter