I would hire more IRS tax collectors to close the tax gap. The tax gap is made up of people who fail to file and report. But it's also made up of people that file but fail to pay. In fact congress might consider doing a tax amnesty. Where tax debts can pay a lowered amount to clear there outstanding IRS debt. The tax amnesty program would be a limited time deal. Like 6 months this is a possible way to get long time tax debtor to voluntary go back to paying their taxes. Generating more income and using it to pay down the national debt.
BTW IRS I'm available if you need a good tax collector in California.