Hi Raju,
Assuming you want accrued interest posting.
This can be achieved through update type SE8701 - Accrued interest pay and SE8702 - Accrued interest receive. Select effective interest calculation check box in update type then you can post accrued interest for purchase and sale transaction.
Update Type - SE8702
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Update Type SE8701
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Purchase transaction
you can select with or without accrued interest calculation for purchase and sale transaction same way.
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For this requirement key date valuation is not required. hope this will solve your issue.