Insights into the structure of main transactions and sub transactions in FSCD.
A transaction is a combination of main and sub-transactions. These combination determines the business process and is used for controlling the business process in the FSCD system. For e.g you can define the FSCD system to collect premium as cash or cheque. Likewise while making the claims payout you can define the payout in terms of transactions as one time claim payout or recurring payouts.
Thus with the help of main transaction and sub transaction the FSCD system recognizes the request for the business transaction.
Main Transaction
The main transaction controls the determination of receivables and payable accounts.
You can view them in the table TFKHVO. You will have to define the values in Customizing to reflect in this table.

Sub Transaction
The sub-transaction controls revenue account determination, determination of the tax determination code, and of information about any additional accounts (business area, CO account assignment data).
You can view them in the table TFKTVO.

Maintaining the Main and Sub Transactions
A user is free to define new entries in this table for use for transactions not defined as ‘internal’ to FSCD. Internal Transactions shall be explained later in detail. These additional main and sub entries can be used in general ledger account determination.
You can also define whether the amount entered can be negative or positive. All postings in FSCD contain information on the business transaction in the main and sub transactions. You can assign additional attributes to the transactions in Customizing.

These attributes are copied in the business partner item when the posting is made and can influence the insurance business transactions.
You can also distinguish between the different receivable types by using different main and sub transactions in the document.
In the below e.g. I have defined my main transaction for Premium by giving the main transaction code as 1000 and in the similar way I can define the main transaction for claims payout as 2000.

Now in the sub transaction section I have defined sub transactions for every main transaction as shown below.

It is very important to note that these transactions are characterized by debit / credit.
The sub transaction is also required for the revenue account determination. This enables you to allocate different revenue accounts to one business transaction (i.e main transaction) by defining special sub transactions. It is also possible to allocate different revenue accounts for each company code and division.
The business area and sales/purchase tax code are defined in revenue account. Further account assignment characteristics (such as cost and profit centers) can be saved there using the CO account assignment key.
Internal Transactions
Internal transactions are those transactions which take place within FSCD.
The main examples of these transactions are charges, interest, payments on account, clarification postings, and so on. These main and sub transactions thus serve to provide parameters needed for the posting of these ‘internal’ transactions.
This function links each item with a main transaction to which several sub transactions are assigned.
For example (with reference to the below screenshots) , there is a main transaction “Charge” and associated sub transactions “dunning charge”, “return charge”, “return charge 1”, “return charge 2”, “correspondence charge”, “installment plan charge”, and so on.


Thus main transactions and sub transactions are used to identify items based on their type (such as interest and charge) as well as the business process from which they originated (payments, account statements, and so on).
Internal transactions are hard coded and are reserved by the FSCD system. Where as external transactions are user defined. For some of the transactions (shown in the above screenshots) which are internal can be assigned to the external transactions.