Maintenance of books of accounts: specified professions and businesses must keep records enabling tax authorities to compute taxable income. Professionals and businesses must maintain books enabling tax assessment: for specified professions (excluding company secretaries and IT where thresholds apply) maintain cash book, journal if using the mercantile system, ledgers, machine- or serially-numbered carbon copies or counterfoils of bills and receipts, original bills and receipts for expenditures, and signed vouchers where appropriate; medical practitioners must keep a daily case register and inventories of consumable stocks. Where income or turnover exceeds statutory limits, books sufficient to enable computation of taxable income are required.