1)Before knowing effect of Venus in 12th house first we have to know about Venus and 12th house. So you may read this
Twelve house-House of expenses
Lord of kaliyug wealth Venus
2)In general way Venus in 12th House is consider very auspicious because it may gives so many good fruits.
3) Venus in 12th house indicating native may be reach and wealthy.As 12th house is also house for expenses and Venus is placed in 12th house indicating native may enjoying luxurious life. But same time native may be cheap and don’t expenses excessively. Native may be highly inclination for getting materialistic profit and he do any karm for getting it.
4)As Venus is karak for sexual relationship and it is placed in 12th house which is belongs to bed pleasure so native is so much inclination regarding sexual activity. Native may gets so much bad comfort even in any position. Native may experts in it.Native may sexual relationship with many women or inclination to making relationship with many women. It may cause for making relationship with low class women.So native may be fallen in the sense of morality.
5)Venus is karak of life partner and it is placed in 12th house so it may causes problem for marriage relationship. Native may face problem through his wife. Wife may have ill health. It may also cause for quarrel between native and his wife. Native may be under control of his wife or ruled by his wife. Native’s wife may be from higher status from native.
6)As Venus is one of eye karak planet and it is placed in 12th house so native may face eye problem.
7)Venus in 12th house indicating native may gets victory over his enemy.
8)Venus in 12th house is also consider bad regarding business. Native may facing financial crisis.