President Joe Biden's Build Back Better Act is likely to end up costing taxpayers about double what the official price tag suggests, and much of that hidden cost will end up being added to the national debt.

That's the conclusion from two independent analyses of the proposal released in recent weeks. Both rely on a key assumption that did not figure into the Congressional Budget Office's (CBO) analysis of the bill: that the Build Back Better plan's various policies will be in place for at least the next 10 years.

"The Build Back Better Act relies on a number of arbitrary sunsets and expirations to lower the official cost of the bill," explains the Committee for a Responsible Federal Budget (CRFB), a nonprofit that advocates for balanced budgets. The group's newly updated analysis of the Build Back Better plan finds that the package will cost an estimated $4.8 trillion over 10 years if all provisions are made permanent—double the price tag applied by the CBO last month.