In the "old days", the income tax filing process was about paying taxes and/or getting back your own over withholding.
Today, it's more about "refundable" credits ; essentially government handouts. The primary one being the "Earned Income Credit" (EIC or EITC).
The basic EIC works on
a "bell curve," rising as a worker's wages rise reaching a maximum
when annual earnings are between $14,000 and $18,350 (Single with 2 or 3
children 2018) and then declining gradually until it phases out altogether. If
your income is on the up slope of the EIC curve more earned income will increase
your EIC but if your income is on the down slope, more income (of any kind)
will reduce you EIC. The “upslope" on the EIC curve is very steep;
basically for every $3 you earn, the government gives you another dollar. See the
curve (graph) at:
http://www.taxpolicycenter.org/briefing-book/key-elements/family/eitc.cfm
The earned income credit is first calculated (actually looked up
in a table) on your earned income then it is calculated on your total income (AGI).
You get the lesser of the two calculated EIC numbers. See the 2018 EIC table
at:
https://taxmap.irs.gov/taxmap/instr/i1040gi-015.htm
