This paper sets out to describe the dynamic nature of the trans-Tasman trade and economic relationship and to develop an approach to quantify the costs and benefits of moving from CER to a wider concept of a 'borderless market'. To examine the dynamic nature of the relationship we have looked at the three relevant periods of modern trans-Tasman integration:  the (past) NAFTA accords;  the current period of CER;  the (future) ideal of a borderless economy. In these periods we have divided each aspect of the relationship into formal (tariffs, quotas etc.), and informal issues (company organisation, business strategy etc). Information for this project was gathered using existing material on trans-Tasman issues, and interviews with businesses. With the help of the ANZBC approximately 20 businesses were surveyed to understand their attitudes towards the trans-Tasman relationship and how it should progress.