Transitional GST rules: treatment of returned duty paid goods, price revisions and refund claims under the GST regime. Section 142 sets transitional GST rules: returns of duty paid goods on or after the appointed day may be treated as supplies when returned by registered persons; price revisions after the appointed day require supplementary invoices, debit or credit notes treated as outward supplies under GST with tax adjustments conditional on recipient reduction of input tax credit; refund claims and appeals initiated before, on or after the appointed day are to be disposed under existing law with any accrued amounts paid in cash, while rejected amounts lapse and balances carried forward are not admissible as input tax credit.