1. From the SAP Easy Access screen, choose Logistics → Materials Management → Logistics Invoice Verification → Document Entry → Enter Invoice (MIRO).
Note: If you are invoking the transaction for the first time, you must
specify a company code in a dialog box.
2. Choose Invoice.
3. In the document header on the Basic data tab, enter the document date, the number of the vendor invoice (reference), and the gross invoice amount, as well as the tax amount with tax code.
4. Then specify the assignment to a procurement transaction. You can reference purchase orders or delivery notes relating to the goods receipts.
5. Enter the number of the document to which the invoice refers.
Note: You can also reference several documents. To do so, choose, with the quick-info text More Assignment Criteria. A dialog box then appears, in which you can enter several document numbers.
6. In the item list, the system suggests all purchase order items that satisfy the assignment criteria specified.and correct the default values if necessary. The items to be posted must be selected (highlighted in yellow).
Caution: The Booking OK indicator in the invoice (transaction MIRO) must not be confused with the OK Indicator of the goods movement (transaction MIGO). With the Booking OK indicator, you can select already checked and processed items.
This indicator has no effect on whether or not the item is taken into account when the invoice is posted.
7. Check whether the invoice is arithmetically correct. This is the case if the balance is zero.
8. Finally, post the invoice.
http://en.vsnew.com/sap-mm-invoice-entry.html