They can request and may be assigned an individual tax ID number (ITIN). Having an ITIN may allow them to open a bank account. It also makes it so they pay taxes which a surprising number want to do. Since they want to stay in the country, having a long history of paying taxes is a way to show you don't want to cause trouble and you just want to work. Hell, a lot of them probably know they got Al Capone on tax evasion and don't want to end up like him. Here's a report I just Googled, and possibly the source of the number which is an estimate.
On the other side is how much tax funding is used on them. Here's a report from the House of Representatives which states they use more in services (Medicare, WIC, sending kids to school, etc) than they pay. I can't speak to how accurate the report is considering the makeup and views publicly expressed by members of the committee. I'm personally leaning towards 'they don't, and can't, use as more than they contribute' because they're not eligible for many benefits.
I love how in your last article it's a human centipede ouroboros
Macgregor said that “every alleged asylum seeker, illegal migrant pouring in through the border in Texas or wherever else” is given a monthly payment of $2,200.
Gheen added that ALIPAC “did not make the original claim about the $2,200,” pointing to Carlson’s interview with Macgregor as its source.
Macgregor cited an article published by a Houston radio station on its website to support the claim he made during the interview, which quotes Gheen and the ALIPAC release. The article was published a week after his interview.
It's explained upthread. You can get an ITIN to pay taxes if you don't have a Social Security Number. The estimate is from the amount collected by the IRS from people with ITINs.