That is awfully quick by the IRS to lien. Now the question is, did he file and not pay,
Or...
Did he not file and not pay.
The latter comes with tax evasion, and is jail time. The former usually comes with just liens.
How they determine the number if he did not file is add up all his income reported to the IRS by various entities, i.e. 1099s from Etrade on stock sales (keep in mind, the IRS will not get cost basis), and will do his taxes for him with no deductions. So, more than likely that number will come down if they did it for him. However, with everything going on, and if he did not file, he may face expect tax evasion charges.