Funds held for clients and corporate investments were as follows:

Included in funds held for clients' money market securities and other restricted cash equivalents as of November 30, 2021 were bank demand deposit accounts and money market funds.

Included in asset-backed securities as of November 30, 2021 were investment-grade securities primarily collateralized by fixed-rate auto loans and credit card receivables and all have credit ratings of AAA. The primary risk associated with these securities is the collection of the underlying receivables. Collateral on these asset-backed securities has performed as expected through November 30, 2021.

Included in corporate bonds as of November 30, 2021 were investment-grade securities covering a wide range of issuers, industries, and sectors primarily carrying credit ratings of A or better and having maturities ranging from December 15, 2021 through September 22, 2028.

Included in municipal bonds as of November 30, 2021 were general obligation bonds, revenue bonds, and pre-refunded municipal bonds primarily carrying credit ratings of AA or better and have maturities ranging from December 1, 2021 through December 15, 2028.

A substantial portion of our portfolios are invested in high credit quality securities with ratings of AA or higher, and A-1/P-1 ratings on short-term securities.

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 the investments held as of November 30, 2021 that had gross unrealized losses of $14.6 million were not impaired due to credit risk or other valuation concerns, and the Company was not required to record a credit loss or an allowance for credit losses on its AFS securities. The Company believes 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 November 30, 2021 and May 31, 2021 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 the COVID-19 pandemic, or changes in the Company’s strategies or assumptions related to any particular investment.

Realized gains and losses on the sale of AFS securities are determined by specific identification of the cost basis of each security. On the Consolidated Statements of Income and Comprehensive Income, realized gains and losses from the funds held for clients portfolio and corporate investments portfolio are included in interest on funds held for clients and other expense, net, respectively. Realized gains and losses from the sale of AFS securities were as follows:

The amortized cost and fair value of AFS securities that had stated maturities as of November 30, 2021 are shown below by expected maturity.

Variable rate demand notes (“VRDNs”) are primarily categorized as due after five years in the table above as the contractual maturities on these securities are typically 20 to 30 years. Although these securities are issued as long-term securities, they are priced and traded as short-term instruments because of the liquidity provided through the tender feature.