Diagnosis
You want to extend an existing commission contract (existing end dateV1; new end date v2). this is only possible if the start date of thenew version of the contract is equal to the existing end date of theexpiring contract.

Procedure
To extend the contract, you must specify the existing effective end dateof the contract as being the effective start date of the new version.
If you wish to change the contract without extending its effectivevalidity, you must specify the existing end date of the contract asbeing the effective end date for the new version.