Situations without UDIs
In many cases, independence is achieved without a declaration of independence but instead has occurred by bilateral agreement. An example of this were the components of the British Empire, most parts of which achieved independence through negotiation with the United Kingdom.
One notable non-declaration of independence has been Taiwan, which is administered by the Republic of China. A formal declaration that Taiwan is independent of China has been one of conditions under which the People's Republic of China would use force against Taiwan. The political status of Taiwan remains controversial, and the position of most supporters of Taiwan independence has been since the Taiwan has never been a part of the PRC, and the governing institutions (of the ROC) function as an independent and sovereign state, there is no need to formally declare Taiwan to be independent. Supporters of Chinese reunification on Taiwan also see no point in a declaration of independence in that they argue that Taiwan is and should be part of a greater entity cultural entity of China, and a new Republic of Taiwan would only bring about a name change in exchange for a communist invasion attempt Taiwan could little afford.
See also: Independence Day, Separatism