The area of XML database outsourcing, whereby the data owner enlists an external service provider to manage the storage and retrieval of their database, has been of increasing interest in recent years due to the relatively inexpensive nature of hardware/bandwidth, compared to the higher expense of in-house expert staff/software. As such it has become increasingly practical to use outsourced database solutions. However, as the service provider may not be fully trusted, XML database outsourcing introduces several security concerns that are new or more complex than those encountered in traditional database implementations. These include: data confidentiality, privacy, secure auditing, query assurance and secure and efficient storage. Of particular importance due to its relevance to most outsourced database models is query assurance - ensuring the database responds correctly to queries. In this paper, we propose the use of temporary time stamps and hash granularity to increase the efficiency of query assurance. This approach is tested against real datasets of varying type and size. Further, we consider how best to create time stamps and the issues associated with expiring versus distributed time stamp models.