IV. (10%) XYZ Corporation, an export oriented company, was able to secure a Bureau of Internal Revenue (BIR) ruling in June 2005 that exempts from tax the importation some of its raw materials. The ruling is of first impression, which means the interpretations made by the Commissioner of Internal Revenue is one without established precedents. Subsequently, however, the BIR issued another ruling which in effect would subject to tax such kind of importation. XYZ Corporation is concerned that said ruling may have a retroactive effect, which means that all their importations done before the issuance of the second ruling could be subject to tax. What are BIR rulings? What is required to make a BIR ruling of first impression a valid one? Does a BIR ruling have a retroactive effect, considering the principle that tax exemptions should be interpreted strictly against the taxpayer?