The Senate Republican tax bill is built on shaky assumptions, such as sunsets of the individual tax provisions that the GOP argues will never actually happen. So the actual cost could be well above the official estimate of around $1.4 trillion — and credible analyses of the bill estimate that the additional revenue it creates through economic growth won't come close to offsetting that cost.
Note: "Likely cost" assumes the bill's sunsets and tax increases will not take effect; Reproduced from Center on Budget and Policy Priorities; Chart: Axios Visuals