I couldn't find anything on the provider website, but thought it might be an HMRC rule. I haven't made the transaction yet, I'd do it now if I knew it would be in this tax year but if that isn't possible would rather wait until we are into new tax year proper to avoid getting in trouble with HMRC (or worse, being on hold for hours to speak to someone who doesn't know and then getting in trouble anyway). Thanks never give up.