5.3 Increase in the Debt Book In relation to the debt book, the Commissioner highlighted that the debt book grew 23% year-on-year to R85.8 billion in 2009/10. For the same period the credit book declined by 7.3% down from R45.5bn in 2008/9 to R42.2bn in 2009/10. The Credit Book is a reflection of payments to SARS which have not yet been allocated.