OBJECTIVES: The introduction of bio-similars to the biologic market has been predicted by market-analysts to save the healthcare systems of Europe and the USA up to $110bn, over the next five years [1]. However, there has been confusion around the ‘least costly’ option available to clinicians in the treatment of conditions such as Rheumatoid Arthritis and Ulcerative Colitis. The objective of this work is to determine the financial impact associated with the introduction of bio-similars, and clarify whether or not their implementation represents a cost saving in comparison to continued use of established biologic medicines. METHODS: A simple one-year budget impact model was developed to assess and characterise some of the costs that may be incurred from switching from an originator biologic (Remicade), to a bio-similar. The recent NICE technology appraisal adoption resource on introducing biosimilar versions of infliximab [2], informed model inputs, and enabled targeted sourcing of cost parameters. RESULTS: The results display that when both products are at no discount, there are no savings involved in switching treatment options. The costs attributed to patient selection, and contacting the patient in order to change treatment options, total approximately £90 for each patient, and the costs of dose adjustment, and those related to the implementation of a treatment, total over £2,000. It can be seen that a change from an originator medicine to a bio-similar, only represent a saving when the discount is greater than the financial impact incurred from the change. CONCLUSIONS: The model demonstrates, due to the financial implications associated with changing from originator biologics to bio-similars, the switching process is more complicated, and costly, than simply interchanging generic medicines. [1] A.Ward,“Copycat drugmakers team up to help UK make more use of cheaper drugs,”17.April.2016.[Online].Available:http://www.ft.com/cms/s/0/398f5e6a-0324-11e6-99cb-83242733f755.html#axzz4AnqRRebk.[Accessed 06 June 2016] [2] NICE,“NICE technology appraisal adoption support for introducing biosimilar versions of infliximab:Inflectra and Remsima,” 31.July.2015.[Online].Available:https://www.nice.org.uk/guidance/ta329/resources/nice-technology-appraisal-adoption-support-for-introducing-biosimilar-versions-of-infliximab-inflectra-and-remsima-493818736/chapter/1-Introduction.