When you have to declare the initial purchase price of a UK property for a Spanish document do you apply the euro rate at the time of purchase?

If you are talking about the Form 720 asset declaration, you use the rate on 31 December of the year for which you are declaring.

It is not for 720. It is CGT. So I need the purchase price.

Logically, a gain will have been in GBP and the exchange rate at the time of the gain would be applied to the gain. What document do you have that askes for the purchase price in Euro?

It is for a divorce and we are Spanish residents. My wife gets the Spanish apartment and I get the UK property. However the UK property has a far greater value than Spanish one so I need to compensate her. Now that is all fine but for me to own the UK property 100% she effectively is giving me her 50% share and the Spanish taxman needs to know if the property in UK has increased in value since we purchased it ( which it had) because then her half has a gain which is subject to CGT even though no sale has gone through. So that means they use the purchase price on the deeds and a present valuation ( no idea how that is done as in Spain they use the cadastral). So I assume they want the purchase price in euros to check that against the 720 ( as that is what my lawyer said was required for 720).

I would use the Euro value on the most recent Form 720 declaration, which would be the purchase price (unless there has been a more recent official valuation).

As for assessing the current price for CGT, it is normally the sale price. In this case there is no sale price which creates a problem. It is going to be your wife's problem as she is the one liable for the CGT. Personally I would expect her lawyers to come up with the most advantageous way of valuing it as its in her interests to use the lowest figure.

On a matter as complex as this, I think professional advice is needed.

Yes I have booked an appointment with my lawyer on Friday
It is just I find the more you have tried to find out the better as often somethings that are obvious to Spanish people are not obvious to foreigners so lawyers automatically assume you understand things without totally explaining it For example, in this case - if my wife pays CGT on her 50% and I then own it 100% what happens if I decide to sell in 5 years time- surely I don't pay full CGT on the whole profit ? Wouldn't it be I only pay CGT on 50% since purchase and then CGT on 50% since the date I got it from my wife ? That seems rather complicated but hey....one thing I found out is do not divorce if you are a Spanish resident because it costs a fortune in taxes and notary fees.!!!

Yes I have booked an appointment with my lawyer on Friday
It is just I find the more you have tried to find out the better as often somethings that are obvious to Spanish people are not obvious to foreigners so lawyers automatically assume you understand things without totally explaining it For example, in this case - if my wife pays CGT on her 50% and I then own it 100% what happens if I decide to sell in 5 years time- surely I don't pay full CGT on the whole profit ? Wouldn't it be I only pay CGT on 50% since purchase and then CGT on 50% since the date I got it from my wife ? That seems rather complicated but hey....one thing I found out is do not divorce if you are a Spanish resident because it costs a fortune in taxes and notary fees.!!!