During the year, an estimated 174 million people had earnings covered by Social Security and paid payroll taxes on those earnings.
A separate projection released on Tuesday showed it will become insolvent in 2034 - the same estimate as previous year.
A major reason for Social Security's long-term financial problems is a decline in the number of workers for each beneficiary.
A companion report by Social Security trustees estimated that the combined trust funds for Social Security, which fund old-age benefits and disability insurance programs, will be depleted by 2034.
Social Security's total cost is projected, for the first time since 1982, to exceed its total income including both tax receipts and interest in 2018 and to remain higher throughout the projection period, the report said.
This would leave the fund depleted by 2034, matching last year's forecast.
But a separate report for Medicare paints a somewhat bleaker outlook for the giant health program for seniors and people with disabilities, estimating that its hospital trust fund will dry up in 2026 - three years earlier than last year's projections.
Still, tax collections would be sufficient to pay about three-fourths of promised benefits for a half-century.
The Medicare Part A hospital trust fund is financed mostly through payroll taxes.
Two other Medicare funds - Part B, which covers doctor and outpatient visits and Part D, which covers prescription drugs - are reset each year based on projected costs. Both will be financed in full indefinitely, but only because the law requires automatic financing of them.
Medicare spending as a percentage of gross domestic product totaled 3.7 percent in 2017, and the trustees project it will increase to at least 6.2 percent by 2092.
"It doesn't mean Medicare is going to go bankrupt in less than 10 years", said Juliette Cubanski, associate director of Kaiser Family Foundation's program on Medicare policy.
In reality, it has been running annual deficits since 2010, and the insolvency date has moved up eight years.As the Social Security crisis keeps getting closer, the political parties are moving further away from doing anything about it.What's scary is that Social Security is relatively easy to fix when compared to Medicare, a program where the rising retirement population is interacting with growing healthcare costs.
Instead any changes made will have to balance who can best afford to pay more or receive less, and how much time they're given to adjust to those changes.
In all cases, however, the longer lawmakers wait, the more dramatic and abrupt the changes will have to be.