Gift Aid on unrestricted and restricted donations

Hello

A question about gift aid and funding streams.

Our charity claims gift aid on eligible donations made to restricted and unrestricted funds.

If the gift aid is claimed against a donation made to a restricted fund, does it also belong in that restricted fund, or can it be added to the general fund?
Is allocation of gift aid a legal requirement or can it be made at the trustees discretion?
If it is a legal requirement, can you point me to the regulations which set this out.

Very grateful for any thoughts or advice on this.

Thank you in advance.

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