I understand what you are saying however the tax deducted was paid to inland revenue in the UK and this was at 20%. I am assuming I need to pay the additional tax as I'm a 40% taxpayer. Just looking at the online assessment form this does not fall into foreign income. Unfortunately I am no further forward in understanding how to claim this.
You are correct in your surmise that this is not foreign income as it was paid under HMRC arrangements. It would therefore be entered in Box 4 [Other dividends]. You just enter the net amount and when submitted the tax with held will be allowed automatically. On filing HMRC will send you a statement indicating any moneys due to or from the Revenue.
The only precaution here is to ensure that HMRC's statement shows that the tax has been deducted at 20% and not limited to the normal notional 10% dividend level.
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Thank you for your support.