While you may not be fined by the authorities for under declaring the property value after two years have passed, your problems may not end there….
What happens if you agree to under declare the purchase price when you buy BUT when you come to sell YOUR purchaser refuses to? The result is that the value of your property, at least on paper and as far as the authorities are concerned, has increased substantially and you will be liable for all the tax on that increase. In effect, you have paid your vendors tax liability for him with absolutely no benefit to yourself.
This is especially the case in a buyers market when you may be struggling to sell and cannot find another buyer who is willing to under-declare by the same amount.
Only my tuppence worth…..