For some RICs it's TR.OFFICIALCLOSEPRICE(e.g. VOD.L), but for others it's TR.OFF_CLOSE(e.g. GS.N). Is there one field that gives me close price regardless of RIC/exchange?
It largely depends on the API that you are using. Try using TR.PriceClose from the reference database.
I am usking eikon py scripting API, does TR.PriceClose include adjustments due to corporate actions?