Upon the death of an account owner, a representative of the decedent's estate usually contacts all firms where accounts are held to begin administering the estate. Part of this process involves obtaining accurate pricing of all assets. With bonds, this process is often more difficult, as many bonds are not traded on an exchange or priced with regularity.
Contact the decedent's financial services firm. Speak with the decedent's financial adviser about determining the date of death valuation for the bonds. Most firms have historical pricing data on many securities, including bonds, and they should be able to find a price for you. Many larger firms have dedicated bond desks, where full-time professional bond traders can reconstruct a bond price, if they don't have direct access to the actual price.
Check to see if the bonds are publicly traded. Although most bonds trade directly between bond traders on a secondary market, some bonds, particularly those from larger, multinational corporations, do trade on an exchange. Look in large financial services newspapers, such as the Wall Street Journal, or online for bond quotes and symbols. The Financial Industry Regulatory Authority (FINRA) operates a general education website for investors that also lists publicly traded bond prices.
Make an estimate using the decedent's statements. You can make a fair market estimate based on the brokerage statements for the decedent's account. This is particularly effective if the decedent's firm issued monthly statements. Simply compare the closing price from the month before the account owner died with the closing price for the following month, and you can develop an effective price range for the bonds. You can also check historical financial news to see if there were any major market movements during the month in question, which may help you modify your estimated price. While not as precise as getting a direct quote, in instances where exact information is unavailable, estate administrators are allowed to make their best good faith estimate.