The IAccount and IAccountData interfaces now expose an OpeningAccount property. If set, this is used for booking the account's opening entries to a different account when an accounting year is closed.

Note that:
1. The OpeningAccount property is only available on accounts of type Status. Setting it to a non-NULL value on any other account type will give you an exception.
2. The value - which is itself an account - has to be of type ProfitAndLoss or Status.

If you're using .NET, to access this property, you'll have to use the latest version of our .NET assembly - which is available here.