Let’s say you’ve initially measured your assets using the depreciation method. This means that the cost of the asset is subsequently expensed showing also the “drop in its value” and in essence what you’ve been doing so far is distribute the expense of the investment over the period it’s being used. 

As a reference, revaluation is a treatment of PPE items where instead of simply depreciating them, you in addition compare its book value with its fair value and you do it as often as the fair value changes (or there are indications of change). Any differences are treated as revaluation gains or losses.

Your list of actions to take should you decide to revalue your PPE items (or specified classes of assets):

1. Decide on the following – which items are to be valued (note that you must opt for revaluation for the entire class and not just for one asset within the class), when to those revaluations take place (namely how often) and the basis used for valuation (professionals qualified in the field, market value, replacement cost etc.)
2. Once you’ve determined the revalued value for the asset(s), you ought to treat it somehow in the accounting as well. Essentially there are two options:
   1. Accumulated depreciation is eliminated against the gross carrying amount of the asset with the net amount restated to equal the revalued amount;
   2. Accumulated depreciation is restated proportionately with the change in the gross carrying amount of the asset such that the net book value of the asset after revaluation equals its revalued amount.
3. Keep up with the fair value of your assets and accordingly if need be, recognize the gains or losses from the differences.

Opting for a revaluation model means that there’s this extra bit of work either every year, once every two years or so on. If you need to revalue assets often than once a year, it may be possible the revaluation model isn’t best suited for this type of assets or in your business environment. Please also note that it’s not just the timeframe you determine when opting for the model, but also indications, which cast doubt on the current fair value being accurate.