HI Prabakaran
Follow the process.
1) Go to Business Partner>Internal Reconciliations>Reconciliation
2) Select reconciliation type, Date and Business partner for whom the accounts are to be reconciled.
for further details refer following links
Reconciliation - SAP Business One 9.0 - SAP Library
BP Internal Reconciliation - Selection Criteria: Manual - SAP Business One 9.0 - SAP Library