自《全国法院民商事审判工作会议纪要》以来，各类增信措施逐渐受到立法及司法的关注。“最高人民法院关于适用《中华人民共和国民法典》有关担保制度的解释”第36条对增信措施法律性质的辨明提供了指引，但该指引并未完全完全消除有关增信措施的疑虑，部分学者不认可所谓独立合同的法律性质，主张未被界定为保证或债务加入的部分增信措施应构成非典型保证。本文选取差额补足承诺这一典型增信措施为研究对象，将没有明确主债务人的差额补足承诺也纳入研究范围。对其常见应用场景加以梳理后，根据基础交易系有明确债务人的融资场景或无明确债务人的投资活动以及差补义务人是否参与投资活动将其分为三类：第一类系有明确债务人的融资场景下的差额补足承诺，第二类系无明确债务人类型下由劣后级受益人提供的差额补足承诺，第三类系无明确债务人类型下由投资活动外的第三方提供的差额补足承诺。以保证的各项特征为标准，进一步辨明不同类型差额补足承诺的法律性质。因缺少具体的主债务及明确的主债务人，第二、三两类差额补足承诺不满足从属性；但将（优先级）受益人的预期投资收益视为主债务，将“投资产品”（信托、资管产品以及有限合伙企业）拟制为主债务人，第二、三类差额补足承诺与第一类无异，均符合补充性、无偿性与单务性以及扩张责任财产以保障债权切实实现性之特征。因此，第一类差额补足承诺或构成典型保证或构成债务加入，但第二、三类差额补足承诺因为符合其他保证特征但不满足从属性，故应当被定性为“非典型的人的担保”。构成保证或债务加入的第一类差额补足承诺当然适用保证及债务加入的相关制度；因此，后文研究聚焦于第二、三类差额补足承诺对于担保制度的适用。关于第二、三类差额补足承诺对于担保制度的适用，首先，作为非典型的人的担保，其无需进一步分析更类似于一般保证或连带保证。关于差额补足承诺的责任范围，出于对差额补足义务人的保护及投资者自担风险的原则，对差额补足义务的履行约定的违约责任对差补义务人没有约束力。关于公司对外担保的决议要求，第二、三类差额补足承诺均应受决议前置要求的约束。关于保证期间，如当事人之间约定了差补义务的履行期间，则可以视为双方对“保证期间”有约定，应予尊重；如未约定，六个月的法定保证期间适用于第三类即第三方提供的差额补足承诺，而不适用于第二类。因为非典型的人的担保中主债务人系由投资产品拟制，故追偿权、抗辩、抵销或撤销权都不适用。

Since the Minutes of the National Court Work Conference on Civil and Commercial Adjudication, various credit enhancement measures have gradually attracted legislative and judicial attention. Article 36 of the Interpretation of the Supreme People‘s Court on the Application of the Civil Code of the People‘s Republic of China on the Guarantee System provides guidance on the identification of the legal nature of credit enhancement measures, but this guidance does not completely eliminate doubts about credit enhancement measures, and some scholars do not recognize the legal nature of so-called independent contracts, claiming that some credit enhancement measures that are not defined as guarantees or debt additions should constitute atypical guarantees.In this paper, the typical credit enhancement measure of the deficiency top-up commitment is selected as the research object, and the shortfall top-up commitment of the principal debtor is also included in the scope of research. After sorting out its common application scenarios, the underlying transaction is divided into three categories according to whether the underlying transaction has a financing scenario with a clear debtor or does not have a clear debtor‘s investment activities, and whether the difference obligor participates in investment activities: the first type is the deficiency top-up commitment under the financing scenario with a clear debtor, the second type is the deficiency top-up commitment provided by the inferior beneficiary under the unspecified debtor type, and the third category is the deficiency top-up commitment provided by a third party other than the investment activity under the unspecified debtor type.Taking the characteristics of the guarantee as the standard, the legal nature of the undertaking to make up the difference between different types is further identified. Due to the lack of a specific principal debt and a clear principal debtor, the second and third types of deficiency top-up commitments do not satisfy the subordinate attribute; However, the expected investment income of the (priority) beneficiary is regarded as the main debt, and the "investment products" (trusts, asset management products and limited partnerships) are proposed as the main debtor, and the second and third types of deficiency top-up commitments are no different from the first category, all of which meet the characteristics of complementary, gratuitous and single-matter, and the expansion of liability assets to ensure the practical realization of claims. Therefore, the first type of deficiency top-up undertaking either constitutes a typical guarantee or constitutes a debt addition, while the second and third types of deficiency top-up undertakings should be characterized as "atypical person‘s guarantee" because it meets other guarantee characteristics but does not satisfy the subordinate attribute. The first type of deficiency top-up undertaking that constitutes a guarantee or debt accession is of course subject to the relevant regime of guarantee and debt accession; Therefore, the following research focuses on the application of the second and third types of deficiency top-up undertakings to the guarantee system.With regard to the application of the second and third types of deficiency top-up undertakings to the guarantee regime, firstly, as a guarantee by an atypical person, it does not require further analysis and is more similar to a general guarantee or a joint and several guarantee. Regarding the scope of liability for the deficiency top-up obligation, out of the principle of protecting the obligor of deficiency top-up and the investor‘s own risk, the liability for breach of contract in the performance of the deficiency top-up obligation is not binding on the obligor. Regarding the resolution requirements of the company‘s external guarantee, the second and third types of deficiency top-up commitments shall be subject to the pre-resolution requirements. Regarding the guarantee period, if the parties agree on the performance period of the deficiency obligation, it can be regarded as having agreed on the "guarantee period" between the two parties and should be respected; If not agreed, the six-month statutory warranty period applies to the third category, i.e. a commitment to make up the difference provided by a third party, and not to the second category. Since the principal debtor in the security of an atypical person is made up of an investment product, the right of recovery, defence, set-off or avoidance does not apply.