Read this directly from the SSA : https://www.ssa.gov/pubs/EN-05-10069.pdf
What income counts…and when
do we count it?
If you work for someone else, only your
wages count toward Social Security’s
earnings limits. If you’re self-employed,
we count only your net earnings from
self-employment. For the earnings
limits, we don’t count income such as
other government benefits, investment
earnings, interest, pensions, annuities,
and capital gains. We do count an
employee’s contribution to a pension
or retirement plan, however, if the
contribution amount is included in the
employee’s gross wages.
If you work for wages, income counts
when it’s earned, not when it’s paid. If
you have income that you earned in one
year, but the payment was made in the
following year, it shouldn’t be counted
as earnings for the year you receive it.
Some examples are accumulated sick or
vacation pay and bonuses.
If you’re self-employed, income counts
when you receive it — not when you
earn it — unless it’s paid in a year after
you become entitled to Social Security
and earned before you became entitled.
