In case of revaluation of assets - all that is required to be done is to assess the remaining useful life of the asset & charge depreciation accordingly.
Step 1: While revaluing the asset the entry would be -
Fixed Assets Dr.
To Revaluation Acc (Part of owner's fund)
Step 2: Now, say the asset was a building originally being depreciated @ 10% p.a. This means the asset's estimated useful life was 10 years. Also, assume the original cost of the building was Rs 100,000. In the past 7 years, depreciation charged is Rs. 70,000. So, the net block of asset becomes Rs. 30,000.
Now, if the assets value is increased by say Rs. 20,000 then the new value of asset in books is Rs 50,000
It is now necessary to ascertain the remaining useful life of the asset. Since, the increase in the value of asset by revaluation must be because the depreciation charged earlier was at higher rate than required.
So, the value of Rs 50,000 should be depreciated over the period of remaining life.