To identify a research gap for the assessment of cash management in banks, you can start by reviewing the existing literature on the topic. You can conduct a systematic literature review to identify the research that has been done so far, and identify the limitations of the existing studies. Here are some steps you can follow:

1. Conduct a search: Start by conducting a comprehensive search of relevant databases, such as Google Scholar, JSTOR, EBSCO, or any other databases that may be relevant to your research. Use keywords related to cash management in banks, such as "cash management," "liquidity management," "cash flow management," "financial management," and "banking."

2. Evaluate the literature: Evaluate the literature you have collected by reading through the abstracts and full-text articles. Look for research that has been done on cash management in banks, such as case studies, surveys, and empirical studies. Take note of the research methods used, the sample size, and the findings of each study.

3. Identify gaps: Identify any gaps in the literature. Look for areas where there is a lack of research or where existing research has limitations. For example, there may be a lack of studies on cash management in small banks, or studies that compare the effectiveness of different cash management strategies.

4. Develop a research question: Based on the gaps you have identified, develop a research question that addresses one or more of the gaps in the literature. For example, your research question could be "What are the most effective cash management strategies for small banks?" or "What factors influence the success of cash management strategies in banks?"

By following these steps, you should be able to identify a research gap that you can address in your study on the assessment of cash management in banks.