NO.PZ2016012102000188
问题如下：
If D.C company had a deferred tax asset of 1.6 million and a deferred tax liability of 1.4 million on its books in December 31, 20X7, but established a valuation allowance of 0.4 million in December 31, 20X8( all other things being equal). What was most likely happened during the 20X8?
选项：
A. It is likely that 0.4 million of the deferred tax liability's value will never be reversed.
B. It is likely that 0.4 million of the deferred tax asset's value will never be reversed.
C. It is likely that 0.4 million of the deferred tax asset's value will be a temporary difference.
解释：
B is correct.
It is likely that 0.4 million of the deferred tax asset's value will never be reversed, because of earning power is decrease and DTA is not be realized, so DTA will decrease by 0.4 million, its treated as valuation allowance.
考点： valuation allowance的含义
由于盈利能力下降，公司发现自己的40万DTA很可能永远都不会转回了，所以需要确认40万valuation allowance，冲减DTA的账面价值。
valuation allowance是deferred tax assets的抵减项，也就是DTA不能回转的时候（直白地说就是该部分税务局欠你的税金，未来没有机会抵扣的时候），就会产生valuation allowance。
在这道题目里面，题干中提到：“established a valuation allowance of 0.4 million in December 31”。也就是说有0.4millionDTA未来无法抵税，所以B选项是对的。
A说是0.4 million DTL没有办法转回是错的，应该是DTA，不是DTL
C说是0.4 million 是暂时性差异，也是错的。因为valuation allowance很可能再也转不回来了可能是永久性差异。
在什么情况下会出现题目这种既有DTA又有DTL的情况呢？两者为何不能抵扣？
