The classification of funds held for clients and corporate investments on the Consolidated Balance Sheets is as follows:

Funds held for clients’ money market securities and other cash equivalents is collected from clients before due dates for payroll tax administration services and employee payment services and is invested until remitted to the applicable tax or regulatory agencies or client employees. Based upon the Company’s intent and its contractual obligation to clients, these funds are considered restricted until they are remitted to fund these client obligations.

The Company’s available-for-sale securities reflected net unrealized gains of $116.9 million and $100.0 million as of August 31, 2020 and May 31, 2020, respectively. Included in net unrealized gains as of August 31, 2020 and May 31, 2020, were 7 and 19 available-for-sale securities in an unrealized loss position, representing less than 1% and approximately 2% of the total securities held, respectively. The available-for-sale securities in an unrealized loss position for which a credit loss has not been recognized were as follows:

The Company regularly reviews its investment portfolios to determine if any investment is impaired due to changes in credit risk or other potential valuation concerns. The Company believes that the investments held as of August 31, 2020 that had gross unrealized losses of $0.2 million were not impaired due to credit risk or other valuation concerns and was not required to record a credit loss or an allowance for credit losses on its available-for-sale securities. The Company believes that it is probable that the principal and interest will be collected in accordance with contractual terms, and that the unrealized losses on these securities were due to changes in interest rates and were not due to increased credit risk or other valuation concerns. Most of the securities in an unrealized loss position as of August 31, 2020 and May 31, 2020 held an AA rating or better. The Company does not intend to sell these investments until the recovery of their amortized cost basis or maturity, and further believes that it is not more-likely-than-not that it will be required to sell these investments prior to that time. The Company’s assessment that an investment is not impaired due to credit risk or other valuation concerns could change in the future due to new developments, including developments related to COVID-19, or changes in the Company’s strategies or assumptions related to any particular investment.