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Why I cannot find a “Pure Cash” option in 401k investments?
Technically there could be a true cash fund, but the issue is it would need to have some sort of cost associated with it, which would mean it would have negative yield or would charge a fee.  In some cases, this might be preferable to having it invested in "cash equivalents," which as you note are not cash.  It is important to note that there is nothing, even cash or physical precious metals, that is considered zero risk.  They all just have different risks associated with them, that may be an issue under certain circumstances.  In severe deflation, cash is king, and all non-cash asset classes and debt could go down in value.  Under severe inflation, cash can become worthless. One respondent mentioned an alternative of stopping contributing to a 401k and depositing money in a bank, but that is not the same as cash either.  In recent decades, people have been led to believe that depositing your money in the bank means you hold that in cash at the bank.  That is untrue.  They hold your deposit on their books and proceed to invest/loan that money, but those investments can turn sour in an economic and financial downturn.  The same financial professionals would then remind you that, while this is true, there is the Federal Deposit Insurance Corporation (FDIC) that will make you whole should the bank go under.  Unfortunately, if enough banks went under due to lack of reserves, the FDIC may be unable to make depositors whole for lack of reserves.  In fact, they were nearing this during the last financial crisis.  The sad thing is that the financial industry is bias against offering what you said, because they make money by using your money.  Fractional reserve banking.  You are essentially holding IOUs from your bank when you have money on deposit with them. Getting back to the original question; you could do some searching and see if there is an institution that would act as a cash depository for physical cash in your IRA.  There are IRA-approved ways of holding physical precious metals, which isn't all too different of a concept from holding physical cash. 401k plans are chosen by your company and often have very limited options available, meaning it'd be unlikely you could ever hold physical cash or physical precious metals in your 401k.