Statistical versus "Real" CO account assignments
Why does SAP talk about statistical assignments in CO  why are these different from
real Cost Accounting assignments ?
The reason is to facilitate reconciliation between FI and CO. The sum of all 'real'
assignments in CO should add up to the sum of all expense and revenue postings (where
cost/revenue elements have been created for the GL account of course) in FI. A
normal expense invoice posting to expense accounts / cost elements will be a 'real'
posting. If the system is displaying an error message insisting on a 'cost accounting
assignment' and you think you have entered one, then possibly you have specified a
statistical assignment. A common error is in thinking that the business area will do 
Business areas are FI elements not CO elements.
Note that the word 'statistical' occurs in a number of different contexts which can
be confusing. We are not talking about key figures here.
So how do 'statistical' postings come about? Strictly speaking the whole document
is not 'statistical' but one or several of the cost accounting assignments on a line item
may be statistical. SAP have defined a number of 'rules' which determine what is
statistical and what is not. Briefly these are as follows:
All Profit Centre assignments are statistical 
ECPCA is defined as statistical, therefore if posting to a
revenue element, the system will insist on a real cost accounting assignment even if
profit centre is specified. A cost centre will not do, since revenue elements are
statistical in cost centres. The system will accept the following as 'real' : COPA
profitability segment, sales order, customer project or a revenue bearing order. 
An assignment to a statistical internal order will be
'statistical'  sounds obvious doesn't it! 
The system will continue to demand a cost accounting
assignment until a nonstatistical assignment is made. For example a cost centre as
well as the statistical order. 
Revenue elements assigned to cost centres will always be
statistical 
'Revenue' when defined to the system by setting up a revenue
element is always statistical in a cost centre. If however you have setup your
revenue accounts as primary cost elements then the assignment will be 'real'. 
Specifying multiple 'real' cost accounting assignments 
If you assign to more than one 'real' account assignment
objects (usually only allowed where one is a cost centre), then one of them will be made
statistical  the cost centre 
The CO cost and revenue element module is where you find the reconciliation
ledger. There are some standard reports that will list by 'object type' (cost
centre, order etc) the CO postings (real assignments) against the FI postings for a cost
element.
Any differences should be due to the use of CO reposts, or distributions, or late setup
of cost elements once postings have been made to a GL expense account.
