Transitional credit to be written off

a) XYZ Pvt. Ltd.  have unutilised balance in Excise PLA A/c from F Y 2014-15 onwards under Education Cess and SHEC. Post GST XYZ also applied for refund through ACES portal, but did not receive the refund. Whether this amount is required to be written off in the books of accounts? The statutory auditors want confirmation on the same. b) XYZ paid service tax under RCM as per Excise Audit of Apr-16 to June-17 with interest & penalty. This amount could not be claimed post GST introduction. Whether this amount to be written off in books of accounts or to keep under receivables? The statutory auditors want confirmation on the same. Please guide.