## 1 Introduction  
With the Fourth Industrial Revolution, digital technologies have reformed how companies conduct business [1]. Following the advancement in the digital economy and the emergence of big data, cloud computing has become a popular choice of technology for reducing processing burdens on users. Broadband network access and on-demand services provide many advantages, including scalability, availability, and reduced hardware and maintenance expenses [2, 3]. Cloud computing has gained immense significance, and may generate investments, employment opportunities, and tax revenues [4]. Furthermore, the implementation of cloud software enables the creation of novel business models [4]. Cloud computing allows enterprises to pay on demand instead of developing applications on in-house data centers [5]. By purchasing cloud software, enterprises can extend their service portfolio without the need for an in-house software development department. However, despite the considerable benefits and opportunities associated with cloud services, security, privacy, and trust concerns have hindered cloud technology's potential utilization and mass deployment [3, 5, 6]. Research reveals that trust issues in cloud computing arise because the data are no longer regulated by the companies themselves, and are instead managed by second or third parties [6]. The trust challenges that arise for companies can be divided into compliance and cost challenges. Enterprises have to meet the compliance requirements defined by the International Standards Organization (ISO) 27000-series, British Standard (BS) 7799, Payment Card Industry Data Security Standard (PCI-DSS), Information Technology Infrastructure Library (ITIL), or Control Objectives for Information and Related Technology (COBIT) [7]. However, enterprises have limited control over whether the requirements stipulated in their standards are implemented using cloud services. Enterprises must trust cloud providers to ensure that agreements are fulfilled as negotiated and that the provided data will not fall into the wrong hands. This trust includes, for example, the specified data storage location. The enterprise must trust that all of its data will be stored as contractually agreed. In addition to the challenges experienced in compliance, there are planning challenges--especially in terms of the planning of costs. Hidden costs can also negatively impact the adoption of cloud services [8]. If, for example, enterprises' compliance requirements require changes (e.g., the data storage location has to be reselected, the backup frequency is changed, or design adaptations must be made), this will incur costs. Changes in cloud applications are typically commissioned via consultants for the application [9]. Enterprises communicate their changes to the cloud service consultants. The consultant consequently passes on these change requests internally, or implements them on behalf of the customer. Adaptations are routinely associated with costs for the consultant service, as well as a time delay [10]. A survey of 250 IT managers in 2015 revealed that over 70% of all companies that relied on additional cloud services were confronted with unforeseen or unexpected costs [11]. Unexpected expenses can thereby easily double the initial budget [12]. Transparency is an important mechanism responsible for removing the trust barrier between enterprises and cloud application providers [13]. In a broader context, this article addresses trust issues in cloud technologies. Within the area of trust, this study focuses on compliance requirements. In particular, it focuses on the transparency, traceability, and automation of recurring cloud compliance adjustments for increased specificity. This study presents a blockchain-based reference architecture and a business process that allows compliance adjustments to be costed transparently, automated without consultants, and made traceable using unique blockchain-based evidence.