There is no legal limit on the amount of foreign currency you can bring into Tanzania, but you are strictly required to declare any amount exceeding $10,000 USD (or its equivalent) upon arrival. This declaration is made to the Tanzania Revenue Authority (TRA) at the customs desk. Failure to declare large sums can result in the seizure of the funds and potential legal penalties. For most tourists, it is highly recommended to bring U.S. Dollars, as they are widely accepted for visas, safaris, and high-end hotels. However, there is a very important "hidden rule" in Tanzania: U.S. bills must be printed after 2006 (and preferably after 2013) and be in pristine condition (no tears or markings). Many banks and local vendors in Tanzania will refuse older bills due to fears of counterfeiting. While you can use credit cards in major hubs like Arusha or Zanzibar, cash remains the primary currency for tips, local markets, and smaller lodges. It is also wise to carry a mix of denominations, as getting change for a $100 bill in a rural village can be nearly impossible.