Why there is difference between MC$4 and FK10N Values.
If I compare the debit amount from FK10N with Invoice amount figure from MC$4 for a prticular period there is huge difference.
What is the basic fictionally between these two and If I want to see the actual invoice amount for a particular vendor then which transaction it would be.
Those tcodes exist in two different modules so they give you different views of the world. MC$4 exists in the MM world. For us when we put in a period in that world, it is calendar based. So 09/2010 means September 2010. This report ONLY shows purchase order related information. So when it defines open, it refers to the PO not being invoiced yet - the PO is open. So try to experiment in your test system where you may not have a lot of POs created. Focus on just 1 vendor. When I enter a month under the Period to analyze, I will get in my results: POs that were created in that period. It will list out how much related to those POs that have been received and invoiced. The report displays PO value, GR value, and Invoice Amount.
Now FK10n resides in the FI world and is document posting date driven. It takes into account not only PO related invoices, but all non PO related invoices, recurring payables, HR 3PR, etc. It is a more complete view of what is hitting your vendor account.
It is also driven by Fiscal Year and not necessarily Calendar Year. For us our Fiscal Year runs from July - June, so 09/2010 would translate to in the fiscal year March 2010. When I run this report, I can see the Sales/Purchases in a certain period. If I doubleclick on a specific value, it takes me to an FBL1n view and only shows the invoices that POSTED in that period. This view shows the FI doc number, if you want to trace it back to the PO, you need to drill down on the 51 number and then go to the menu and select Environment\Document Environment\Original Environment.
Hope that helps clarify,