Unpaid Seller (Sections 45-54) is seller who has not received payment or accepted bill of exchange. Rights: (1) Lien—retain possession until payment; (2) Stoppage in transit—intercept goods in transit if buyer insolvent; (3) Resale—sell goods if buyer defaults. Lien requirements: (1) Part/full payment not received; (2) Goods not delivered; (3) Sale not on credit/credit period expired. Lien loss: Delivery, acceptance by buyer, waiver by seller. Stoppage in transit: Seller can stop goods while in transit if buyer becomes insolvent. Transit ends when buyer obtains possession or carrier agrees to buyer. Resale: After lien/stoppage, seller can resell; seller not liable for loss unless bad faith. Notice: Seller should notify buyer of stoppage/resale. Case law: Ogg v. Shuter establishes lien scope. For accountants, unpaid seller rights affect when inventory relief occurs and whether bad debts provisions needed. Understanding rights protects seller interest in insolvency. Exam tip: Identify if seller unpaid; determine which right applies; assess notice and timing requirements.