预付款保函也称为还款保函（Repayment Guarantee），在买卖合同下还可以称为定金保函（Down Payment Guarantee）。是指担保人应合同一方当事人的申请，向合同另一方当事人开立的保函。保函规定，如申请人不履行他与受益人订立合同的义务，不将受益人预付或支付的款项退还或还款给受益人，担保人向受益人退还或支付款项。预付款保函对应的英文为“Advanced Payment Guarantee”：A contract under which the issuer undertakes to be responsible for the fulfilment of a contractual obligation owed by one person to another if the first person defaults. The issuer's obligation may be primary (as in an on-demand obligation or indemnity) or secondary (as in a guarantee). An advance payment guarantee or bond is typically used to underpin or guarantee the performance of a commercial contract, such as a contract for the sale of goods (where the buyer is the beneficiary) or a construction contract (where the employer is the beneficiary).

预付款保函在国际承包业务中使用时，是由承包人通过银行向业主提供。保证书规定，如申请人不履行他与受益人订立的合同的义务，不将受益人预付、支付的款项退还或还款给受益人，则由银行向受益人退还该款项。

预付款保函除在国际工程承包项目中使用外，也适用于货物进出口、劳务合作和技术贸易等业务。例如，在成套设备及大型交通工具的合同中，通常采用带有预付性质的分期付款或延期付款支付部分价款。在这种交易中，进口人在签订合同后，向出口人开立履约保证书，由银行保证进口人按合同规定按期支付价款，同时，出口人也向对方开立还款保证书。如出口人不能按期交货，银行保证及时偿还进口人已付款项的本金及所产生的利息。

以下为某一公司发出的预付款保函，供参考：

ADVANEC PAYMENT BANK GUARANTEE

Contractor Name : []

Address : []

Dear Sirs,

SUBJECT :ADVANCE PAYMENT BANK GUARANTEE NO. :[                                                     ]

                   Date : [                                                 ]

Whereas XX (hereinafter referred to as "Contractor'') has entered into a Subcontract (hereinafter referred to as "Subcontract") with [Subcontractor Entity Name] (hereinafter referred to as the “Subcontractor”) for Subcontract and  whereas Contractor shall effect a payment by way of an advance to Subcontractor against presentation by Subcontractor of a Letter of Guarantee issued by a bank in favor of Contractor as guarantee in respect of such Advance Payment.

Therefore, in consideration of the above, We, [Name of the Bank], established in [Nationality of the Bank] and having our address at [Address of the Bank], hereby irrevocably and unconditionally guarantee and undertake to Contractor, as the primary obligor without any right of defense, set off or counterclaim, whether on our behalf or on behalf of Subcontractor, to pay to Contractor promptly any sum or sum , upon receipt of Contractor’s written demand addressed to us in the event that Subcontractor fails to perform or fulfill any of its obligations repaying the Advance Payment in accordance with the Terms of the Subcontract, by transfer to an account in Contractor’s name at such bank in [Nationality] as Contractor shall stipulate or in such other manner as shall be acceptable to Contractor within ten (10) business days. Such written demand shall be conclusively binding on us for all purposes under this Advance Payment Bank Guarantee. The terms “business day” shall mean a day on which banks are open for business in [Nationality].

We agree that any payment made hereunder shall be made free and clear of, and without deductions for or on account of, any present of future taxes, levies, imposts, duties, charges, fees, deduction so or withholdings of any nature whatsoever and by whomsoever imposed.

This Advance Payment Guarantee shall be governed by and interpreted under the laws of England and Wales and shall be subject to the Uniform Rules for Demand Guarantees of the International Chamber of Commerce(Publication No. 458), except as stated above.

Unless settled amicably, the dispute shall be finally settled under the Rules of Arbitration of the International Chamber of Commerce and the seat of arbitration shall be the London.

预付款银行保函

承包商名称：【】

地址：【 】

敬启者：

主题：预付款银行保函  编号【】

             日期【】

鉴于XX公司（以下简称“承包商”）已与【分包商名称】（以下简称“分包商”，就分包【项目名称】签订了分包合同（以下简称“分包合同”）同时鉴于承包商应在分包商提交一 份银行签发的以承包商为受益人的预付款担保函后，应向分包商支付一笔预付款。

因此，考虑到上述情况，我行，【银行名称】（在【银行所在国家】成立，地址为【银行地址】）特此作为没有任何以我行或分包商名义的抗辩、抵消或反请求权利的主要债务人，以不可撤销的方式无条件担保并承诺承包商，在分包商未能履行或未履行其根据分包合同条款偿还预付款的任何义务的情况下，在收到承包商的书面要求后，应在十（10）个营业日向承包商进行支付。在此预付款保函项下，此类书面要求对我行具有最终约束力。“营业日” 一词是指位于【国家】的指定银行营业的日期。

我行同意，本协议项下的任何付款均应免除，且不得扣除任何性质的当前或未来税费、征费、税金、关税、收费、费用，不得扣除任何性质或由任何人施加的预扣款。

除上述约定外，本预付款保函应受英格兰和威尔士法律管辖并据其解释，并须遵守国际商会《见索即付保函统一规则》（第458号岀版物）的规定。

除非友好解决，否则相关争议应根据《国际商会仲裁规则》予以最终解决。仲裁地应为香港。