If you're buying a MHADA flat from the first buyer, and the original allotment/possession letter wasn't registered, you need to understand the implications. While stamp duty was paid, an agent insists on registration (adjudication) which could incur significant costs due to the difference between MHADA's calculated duty and the market rate, plus penalties. This registration is crucial for the eventual conveyance. Consult the Sub-Registrar's office or a lawyer for accurate stamp duty and penalty calculations, and clarify who bears the cost.