Transfer pricing is a company policy in determining transfer prices to other companies, but in practice transfer pricing is done in order to avoid taxes. At present Indonesia has not been able to overcome the issue of transfer pricing because the regulations and sanctions are still unclear. Businessmen as taxpayers need legal certainty in the context of tax planning and business competition, while the government also requires legal certainty to secure revenues from the tax sector. The legal vacuum created legal uncertainty for both parties so that it was not in harmony with the principle of justice. Regulation regarding transfer pricing in Indonesia has actually been regulated in legislation found in Article 18 paragraph (3), (3a), and (4) Income Tax Law. However, the regulation has not been clearly regulating transfer pricing. The unclear regulation regarding transfer pricing lead Indonesian Government to refine the Anti-Avoidance Rule (AAR) which is integrated in the Income Tax Law. The AAR must provide clear definitions and differences regarding acceptable tax avoidance, unacceptable tax avoidance, and tax evasion, so that transfer pricing that breaks arm's length principle will be categorized as illegal. In addition, the AAR must be clearly and explicitly regulated regarding sanctions for transfer pricing doer. Improvement of AAR which is integrated in the Income Tax Law will provides legal certainty and guarantees justice for both businessmen as taxpayers and the government.