联合国范本与OECD 范本中关于第五条“常设机构”的异同
常设机构条款（PE ）确立了在双边税收协定下来源国按照经济参与程度对经营所得征税的水平（类似于居民国对投资所得的征税）。如果来源国对投资利润征税，外国投资者的居民国必须按照税收协定消除双重征税的目标，给予来源国已征税款税收抵免或免税待遇。
一、相同点：
Article 5 of the United Nations Model Convention is based on Article 5 of the OECD Model Convention
OECD 和UN 税收协定范本第五条对常设机构的定义如下：“在本协定中，‘常设机构’一语是指企业进行全部或部分营业活动的固定营业场所”。同时，第五条还采取正列举的方式，明确“常设机构”特别包括：1、营业场所；2、分支机构；3、办事处；4、工厂；5、作业场所；6、矿场、油井或气井、采石场或者其他开采自然资源的场所。
二、不同点：
OECD 税收协定范本和联合国范本相比，主要通过限制来源国的征税权力，将更多的征税权留给居住国。具体如下：
1、there is a six-month test for a building or construction site constituting a permanent establishment, rather than the twelve-month test under the OECD Model Convention, and it expressly extends to assembly projects, as well as supervisory activities in connection with building sites and construction, assembly or installation projects。（对于建筑工地持续期间的测试，联合国范本规定是6个月，而OECD 范本是12个月，这种差异同样适用与建筑工地有关的工程监理、装配或安装等项目的时间鉴定。）
2、the furnishing of services by an enterprise through employees or other personnel results in a permanent establishment where such activities continue for a total of more than 183 days in any twelve-month period commencing or ending in the fiscal year concerned。（对通过雇员或其他个人提供装饰服务的公司，其常设机构判断的标准，联合国范本表述由原来的“在一个开始或结束的财政年度超过6个月”改为“超过183天”。）
3、Article 14 (Independent Personal Services) has been retained,whereas in the OECD Model Convention, Article 14 has been deleted, and Article 5 addresses cases that were previously consid ered under the “fixed base” test of that Article.。（OECD 范本保留了第十四条关于独立个人劳务的条款，联合国范本则将之删除，由此，联合国范本中第五条增加了对被删除的第十四条“固定场所”的注释。）
4、in the list of what is deemed not to constitute a permanent establishment, “delivery” is not mentioned in the United Nations Model Convention, but is mentioned in the OECD Model Convention. Therefore a delivery activity might result in a permanent establishment under the United Nations Model Convention, without doing so under the OECD Model Convention。（在不属于常设机构的列表中，“运输”一词没有在联合国范本中提及，但却体现中OECD 范本中。因此，在联合国范本下，运输活动可导致常设机构，而在OECD 范本下，则不存在这个问题。）
5、the actions of a “dependent agent” may constitute a permanent establishment, even without having and habitually exercising the authority to conclude contracts in the name of the enterprise, where that person habitually maintains a stock of goods or merchandise and regularly makes deliveries from the stock。（独立代理机构如果保留存货并且经常性地运输可以被认定为常设机构，即使合同不是以被代理人名义签订的。）
6、As compared with the OECD Model Convention, the United Nations Model Convention indicates that such an agent devoting all or nearly all their time to a particular client and not dealing with the client at an arm’s length basis is not treated as having the necessary independence 。（联合国范本认代理机构将会把几乎全部精力投入到一个主要客户上，而不会公平独立的对待他，因此这些机构不能被认定为独立代理机构，而与OECD 范本则相反。）
7、there is a special provision specifying when a permanent establishment is created in the case of an insurance business; consequently a permanent establishment is more likely to exist under the United Nations Model Convention approach。（在联合国范本下有个特别的条款，允许和保险有关的特殊情况可以构成常设机构。）
除了上述几点，由于OECD 范本没有条款专门规定劳务的征税权划分，因此，OECD 认为“常设机构构成的征税起点适用于所有的商业活动，包括独立劳务”，而联合国范本拒绝采用这种方式，而是采用OECD 范本注释中少数人的观点：“„„即使对非居民产生的不归属于常设机构的利润征税带来一些遵从和管理上的困难，但是这些困难不应该使得将这些企业在该国管辖区域内所有劳务产生的利润被免税。”