Blackflushing does not mean returning of material to stores. 

With backflush infact the component allocated in BOM get consumed at the time of operation/order confirmation.
 

If you set the backflush then all materials allocated to the Work Order will get issued from stores automatically.  So there is no need to do a separate MB1A or MIGO Goods Issue.

To return item to store you will have to do a reversal from WO back to stores using Movement Type 262.
 

I want to issue spares in advance to engineers without a service work order....Later on the spares will get consumed or will get returned.  How do I do it...and what is the Movement type to be used for issuing and reversing........can any one help.
 

Still I have problem in back flushing. Suppose I made the indicator of backflush in creation of order, then I completed technically, then the actual cost of material not updating, (Note I have not posted the material in MB1A) what is the problem, pls tell me.
 

Did you confirm your maintenance order? Unless you confirm it (IW41) your actual cost will not be updated. Backflushing is a tool so that during confirmation you will not anymore input your
materials. System will confirm your consumption base on the order (IW31) you have created.
 

I believe T-Code IW41 is used to confirm the operation and not for materials.  When backflush indicator is set in the order for the components reserved then MB1A need not be done and when we say determine cost thru the main menu, the material cost should appear.
 

Actually IW41 works like CO11 (PP module), when you tick the backflush indicator in the order creation the system will automatically copy those materials when you confirm it.

Try doing these steps:

1. Create order (IW31)
2. Assign a component to the order and tick the backflush field. (make sure that the component you assign has stock and valuated in the material master - check it thru MM03, accounting and costing fields)
3. Check availability of material and release 
4. Goto IW41, enter hours and tick the material icon on the tool bar (you would notice that the materials that was backflush are already copied in the confirmation, try unticking the backflush icon in IW31 and you would notice that the component field will be empty because no material are backflushed)
5. Save
6. Check cost and it would reflect the material consumed. Actually you don't need to go to the component field for it to confirm your consumption. It will automatically post all materials backflushed upon saving your confirmation in IW41. In short you still need to confirm your order, thru IW41, for the materials to be consumed. MB1A are actually used for set-up where in the one issuing the material to the order are not the same person who is confirming the maintenance order.

I hope this clarifies everything. 
 

Thank you so much.  Yes it works......thanks a ton. 
But I have a suggestion.  I did whatever you said....but what I noticed was once I reserve a component in the order thru IW31 trasanction and release the order and go to main function and say determine cost, the materials cost is automatically copied into the order....Yes the material should exist in the material master.......

I feel in the same order when we want to calculate the labour charges involved in particular operations we need to go thru IW41 and confirm the operations so that we can get the labour charges for the personnal involved in that order.(this will be done by way of calculating the Activity types). 
 

Your right material cost is automatically copied into the order thru IW31 but these costs are only planned cost. Meaning no accounting documents is being created and no materials being consume to the order only reservations. 

If you want to have the actual cost reflected you have to go thru IW41 first.

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