https://www.irs.gov/pub/irs-pdf/f1099r.pdf
Box 5. Generally, this shows the employee’s investment in the
contract (after-tax contributions), if any, recovered tax free this year;
the portion that’s your basis in a designated Roth account; the part of
premiums paid on commercial annuities or insurance contracts
recovered tax free; the nontaxable part of a charitable gift annuity; or
the investment in a life insurance contract reportable under section
6050Y. This box doesn’t show any IRA contributions. If the amount
shown is your basis in a designated Roth account, the year you first
made contributions to that account may be entered in box 11.
