Can some one suggest how can i delete a voucher?
no
U should not delete any posted document. If u required to cancel it, reverse the entries with appropriate description and reason code.
Deletion of posted document is not possible. It would be safer to pass a correction entry, else, somebody might end up deleting the wrong voucher.
You can delete posted documents (invoices and shipments) without any kind of problem. Deleting the posted invoice, posted receipt and/or posted shipment only deletes the record on the corresponding posted document tables, but it doesn’t delete the entries created on the g/l, item,vendor or customer ledger entries. If you’re wanting to cancel a posted invoice the best way is using a standard credit memo.