The number, which is only a slight improvement from the CBO's estimate of the health care bill passed by the House of Representatives in May, comes in the office's analysis of the Better Care Reconciliation Act, a draft of which was released last week.
The act, which faces opposition from Democrats and concerns from at least five Republicans in the Senate — enough to block its passage — could further result in a reduction of the cumulative federal deficit by $321 billion by 2026, largely due to cuts in Medicaid spending, according to the CBO's report.
Decreased Medicaid spending, estimated by the CBO to be a 26 percent cut by 2026 from projections under the current law, was a point of contention for a number of senators when a draft of the plan was released last week. The decrease would result in a 16 percent drop in enrollment for the government-funded program, according to the CBO.
A rollback of Medicaid programs that expanded in some states under the current law would hit people just above the national poverty level the hardest, the CBO estimated.
Close to 40 percent of adults ages 30 to 49 who make less than $24,000 a year (the 2017 poverty threshold for an individual is a little over $12,000) would not have insurance by 2026 under the Senate bill, according to the office's report.
The analysis is the first for the Better Care Reconciliation Act, the draft of which was updated Monday. The CBO analysis reflects a revision that proposes a six-month waiting period for those who want to purchase individual insurance but have let their coverage lapse for at least 63 days.
The Senate plan notably would eliminate the Affordable Care Act's individual mandate, which taxed those who did not purchase insurance, but would add the waiting period for coverage lapses as an incentive for healthier individuals to buy insurance.
The CBO report states that a fair number of younger Americans would likely see their insurance premiums go down if they choose high-deductible catastrophic-coverage plans. Older Americans and people who want to purchase higher-value plans, with lower deductibles or more extensive coverage, could see their premiums increase significantly.
The Republican plan would allow states to apply for waivers from the Affordable Care Act's standards and benchmarks for insurance plans. Through the waiver system, states could let insurance companies offer plans without the ACA's required minimum essential health benefits (EHBs) — maternity care and emergency services among them — and reinstate lifetime and annual caps that are banned under Obamacare.
The CBO estimates that about half the country's population would end up living in states with EHBs waived.
"People who used services or benefits no longer included in the EHBs would experience substantial increases in supplemental premiums or out-of-pocket spending on health care or would choose to forgo the services," the report states.
In a statement Monday, Senate Majority Leader Mitch McConnell of Kentucky pledged that "the Senate will soon take action" on the bill and focused on the CBO's estimates of deficit reduction, tax cuts and lowered premiums.
"The American people need better care now, and this legislation includes the necessary tools to provide it," he said.
The final CBO review of the American Health Care Act, the House's bill, estimated that 23 million more Americans would be uninsured by 2026 than under the current law and that the federal deficit would be reduced by more than $119 billion from 2017 to 2026.