Меняю у уже существующих МВП период действия и все.

The change period must not exceed the limit of the existing periods of validity. If you want to extend an existing period of validity, you must create a new period using ProfitCenter.Create. This period will follow on seamlessly from the current period.

If the change period encompasses several analysis periods, the only data which can be changed for the profit center is that data which is identical in the previous/existing analysis periods. If the required change period lies within a previous analyis period, the new value will be valid in the entire analysis period or, alternatively, the system will create a new analysis period (the latter occurs if the fields you wish to change are time-dependent).