A bond sinking fund is reported in the section of the balance
sheet immediately after the current assets. The bond sinking fund
is part of the long-term asset section that usually has the heading
"Investments." The bond sinking fund is a long-term (noncurrent)
asset even if the fund contains only cash. The reason is the cash
in the fund must be used to retire bonds, which are long-term
liabilities. In other words, because the money in the bond sinking
fund cannot be used to pay current liabilities, it must be reported
outside of the working capital section of the balance sheet.
(Working capital is current assets minus current liabilities.)