Some Senate Republicans are raising concerns about a provision in a mammoth stimulus package unveiled Thursday that would reduce the amount of cash assistance for lower-income individuals."The current bill has promise but it shouldn’t give lower earners smaller checks — that’s directly contrary to my proposal. We need to fix this to ensure lower earners get equal payments," Romney tweeted on Thursday night

Sens.(R-Utah) and(R-Mo.) are pushing for changes to the provision, arguing that individuals with little or no tax liability should get the same $1,200 check that Republicans are promising for individuals who make up to $75,000.

Part of that plan is to give a one-time check of $1,200 to individuals who make up to $75,000. The amount received would then begin to scale down until it reached an income threshold of $99,000, where it would phase out completely. The income levels would be based on 2018 tax returns.

But a GOP summary of the bill noted that individuals with little or no tax liability would receive roughly half — a minimum of $600.

"Taxpayers with little or no income tax liability, but at least $2,500 of qualifying income, would be eligible for a minimum rebate check of $600 ($1,200 married). Qualifying income includes earned income, as well as Social Security retirement benefits and certain compensation and pension benefits paid to veterans. This ensures relief gets to low-income seniors and disabled veterans," the summary reads.