The basic EIC works on a "bell curve," rising as a worker's wages rise reaching a maximum when annual earnings are between $15,400 and $20,150 (Single with 2 or 3 children 2022) 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 2023 curve (graph) at:
See the 2023 curve (graph) at https://crsreports.congress.gov/product/pdf/R/R43805 (page 2)
