how do you treat a revaluation of a fixed asset in the income statement?

Answer 1

You didn't say whether the revaluation resulted in an increase or decrease in the carrying amt of the asset. Here's an excerpt from IAS 16 Property, Plant & Equipment

39. If an asset’s carrying amount is increased as a result of a revaluation, the increase shall be credited directly to equity under the heading of revaluation surplus. However,
the increase shall be recognised in profit or loss to the extent that it reverses a revaluation decrease of the same asset previously recognised in profit or loss.
40. If an asset’s carrying amount is decreased as a result of a revaluation, the decrease shall be recognised in profit or loss. However, the decrease shall be debited directly to
equity under the heading of revaluation surplus to the extent of any credit balance existing in the revaluation surplus in respect of that asset.

So as you can see, you don't always take the difference to the income statement. If the diff is an increase in the value, you take the credit straight to equity under "Revaluation Surplus" UNLESS you have previously recognised a loss for this same asset in the income statement. If so, you take the increase now to the income statement until it reaches the loss previously recognised, then you take the excess credit, if any, to Revaluation Surplus.

If the diff is a decrease in the value of the asset, you take the debit to the income statement UNLESS you have previously taken an increase to Revaluation Surplus for this same asset. If so, you now debit the Rev Surplus with the decrease until you reach the amt previously credited, then you take any excess debit to the income statement.

Let's take the simplest scenario - you revalue an asset which you have never revalued before, so there's no history of any revaluations either in equity or in the income statement. So now, if your revaluation results in an increase in the carrying amt of the asset, take the increase to equity under "Revaluation Surplus", and if it results in a decrease, take the decrease to the income statement.

Answer 2

HOW DO I TREAT A RETAINED EARNINGS IN THE INCOME STATEMENT OR IN THE BALANCE SHEETS?