****UPDATE**** The loss is due to the partial exemption and the advance lump sum to be deducted from the profit. TR support has just informed me of this after a lengthy back and forth.
@Playrio the deducted advance lump sum has been offset against the existing tax-free allowance. As a result, this has increased again for this year. So the loss was initially in the loss calculation pot, was then offset against the advance lump sum and then against the exemption order, which is now almost complete again.
