Washback concerns the impact of tests and assessments on materials, teachers, and learners. 30 years of research has shown that testing and assessment have influenced language teaching significantly. Teaching English as an international language (TEIL) is a quickly developing and practical new reality that is beginning to influence language assessment, and to challenge the use of L1 speaker norms for English language proficiency tests such as IELTS and TOEFL. While the recent, cumulative knowledge of EIL is making those norms increasingly irrelevant, they still have significant impact of World English (WE) users. In this way EIL, which is not bound to a particular variety of English, allows for communication to occur according to context and is at the forefront of change in assessment. Thus, the washback effect in TEIL is driving assessment, while being influenced by the continued power of international language tests.