Statement of Practice SP4/97 (see EIM64605) also covers cases where liability arises under the Trading Income rules . The Trading Income part of the Statement is reproduced in the Inspectors' Manual at BIM40655. Broadly, when commission is received on a regular basis or from a genuinely casual arrangement it may be treated as Trading Income. See BIM40650 onwards and BIM80100 onwards. An unexpected, wholly gratuitous, non-business receipt will not be chargeable to tax as Trading Income.