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HMRC internal manual

Capital Gains Manual

Losses: loans to traders: payments under guarantee

It is likely that in most cases the information suggested above will enable you to decide whether the payment was made under the guarantee. In cases where there is little or no evidence to support the assertion that the payment was under the guarantee and payment went to a person other than the lender, it may be appropriate to refuse the claim on the grounds that the payment was not made under the guarantee. It could instead constitute a loan to the recipient. As such it may potentially qualify for relief under Section 253 (3), but you would need to be satisfied that all the necessary conditions for relief under Section 253 (3) were met, particularly that the loan was recoverable when made, see CG65957.