Oxford Dictionary of Law
Oxford university Press
2006

Warranty:
n. 1. (in contract law) A term or promise in a contract, breach of which will entitled the innocent party to damages but not to treat the contract as discharged by breach. Compare CONDITION. See also INNOMINATE TERMS.
2. (in insurance law) A promise by the insured, breach of which will entitle the insurer to trat the contract as discharged by breach
3. Loosely, a manufacturer's written promise as to the extent he will repair, replace, or otherwise compensate for defective goods; a *guarantee


Guarantee
n. 1. A secondary agreement in which a person (the guarantor) is liable for the debt or default of another (the principal debtor), who is the party primarily liable for the debt. A guarantee requires an independent *consideration and must be evidenced in writing. A guarantor who has paid out on his guarantee has a right to be indemnified by the principal debtor Compare INDEMNITY
2. See WARRANTY



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Note added at 3 hrs (2011-03-27 15:36:29 GMT)
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Bill of sale

(тот же словарь)

A document by which a person transfers the ownership of goods to another. Commonly the goods are transferred conditionally, as security for a debt, and a conditional bill of sale is thus a mortgage of goods. The mortgagor has a right to redeem the goods on repayment of the debt and usually remains in possession of them; he may thus obtain false credit by appearing to own them; An absolute bill of sale transfers ownership of the goods absolutely. The *Bills of Sale Acts 1978 and 1882 regulate the registration and form of bills of sale. The *Civil Procedure Rules set out certain formalities in relation to litigation concerning bills of sale under these statutes.

вот только проблема в том, что в русском праве, например, обеспечить ДОКУМЕНТ нельзя, обечпечивается исполнение ОБЯЗАТЕЛЬСТВА по договору (договор купли-продажи), я бы игнорировала слово "купчая"

Я думаю нужно как-то общо, типа "Sale agreement" Sale and purchase agreement"