Some people have a notion that reducing the national debt will help strengthen Social Security. Any such effect is largely indirect. To the extent that the government has less debt, when Social Security has to cash in some of its accumulated IOUs to pay benefits, the government will find it easier to borrow. So reducing indebtedness now may give the government more resources in the future. They are not authorized to invest in anything but Treasury securities, and it makes no sense to hold cash which earns little or no interest.
Tax cuts are a politically popular but dangerous use of surplus funds.
Certainly the tax code can always stand some improvements, so some modest tinkering with small revenue losses might be justified. But because taxes are easy to cut and hard to raise, any tax cuts financed out of the surplus would be committing the government to lower revenues in the future when spending demands might be higher. In addition, contrary to popular opinion, Americans are not really heavily taxed. And it has not changed very dramatically over the decades. Discretionary spending The third option is to consider whether some spending increases might be justified.