Payment of the tax is linked to an individual's benefits and credited to the Trust Fund, which is just an accounting of "surplus" payroll tax collections. The trust funds were growing but are now depleting as tax revenues are less than outlays.

And yet, if one examines the budget items in question it becomes obvious that no net credit is given for those payments and the entire sum of benefits is subject to the will of Congress to add to the national debt. Treasury bonds do not hold "money" that can be spent on future benefits. They are a "promise to pay" contract with our government that requires new money creation at their maturity to service the debt.

"ALL" revenue of the federal government is applied to reducing the money supply in the private sector, the national debt, and cannot survive that accounting to be applied to any future spending of Congress. This isn't even economics, but simple sectoral balance accounting 101.

This is the origin of the controversy over "lock boxes" from the 2000 election that went away as too revealing to the falsehoods surrounding federal finance to allow to become common knowledge. The only purpose served by SS and Medicare payroll deductions since we left the gold standard is to draw down the spending power of the working class in the private sector.

I began a deep dive into federal finance in an attempt to explain this, but discovered that others have been there with similar purposes. They were the early advocates of MMT, and even a former Fed chairman for FDR who wrote a white paper titled "Taxing For Revenue Is Obsolete" in '45. I have touched on this subject here before. https://oldngrumpy.medium.com/how-the-debt-ceiling-and-social-security-prove-the-common-view-of-federal-financing-is-false-adda8f7a1c51