JB died on March 2000. He left as heirs AV, his surviving spouse and five children. His estate was judicially partitioned. In said order of partition, the heirs were given a 12 hectares of agricultural land. As the five (5) children were minors that time, AV administered the minor's properties and decided to lease the twelve (12) hectares to R Corporation. For 24 years, the said 5 hectares land accumulated Php 20,000,000.00 earnings from the lease and other legitimate investment transactions. From then on, the BIR said that all the heirs of JB formed an unregistered partnership and therefore, subject to corporate income tax. Did JB's heirs formed an unregistered corporation, thereby subject to corporate income tax?