What business expenses are deductible?

You can claim deduction for expenses that are incurred in the production of income. It must also be revenue in nature; the deduction must not be prohibited under the Income Tax Act; and the expenses must be incurred.Examples of deductible and not deductible expenses:
Deductible expenses Not deductible expenses
Accounting fee
Administrative expenses
Advertisement
Auditors’ remuneration
Amortisation
Bad debts (trade debtors)
Bank charges
Book-keeping services
Bad debts (non-trade debtors)
Commission
CPF, skill development levy, foreign workers’ levy
CPF contributions (Voluntary*)
Certificate of entitlement (COE) for motor vehicles**
Directors’ fees
Directors’ remuneration
Depreciation (you may claim capital allowances)
Donations
Entertainment
Exchange loss (trade and revenue in nature)
Exhibition expenses
Entrance fee (country club or other clubs)
Exchange loss (non-trade or capital in nature)
Fixed assets written off
Fixed assets acquisition cost
Fines
Goodwill payment
Impairment loss on trade debts
Insurance (e.g. fire, workmen compensation)
Interest expenses
Impairment loss on non-trade debts
Income tax
Installation of fixed assets
Insurance (certain life insurance)
Interest expenses (interest adjustment)
Legal and professional fees (trade and revenue transactions) Legal and professional fees (non-trade or capital transactions
Medical expenses (restricted to 1% of total remuneration)
Motor vehicle expenses (goods / commercial vehicles, e.g. van, lorry and bus)
Medical expenses (amount exceeding 1% of total remuneration)
Motor vehicle expenses (“S” plate private passenger cars)
Office upkeep
Periodicals & newspapers
Postage
Printing & stationery
Property tax
Provision for bad and doubtful debts (specific)(note impairment loss on trade debts)
Provision for obsolete stocks (specific)
Penalties
Preliminary expenses
Private and domestic expenses
Private hire car
Provision for bad and doubtful debts (general)(note impairment loss on trade debts)
Provision for obsolete stocks (general)
Rental of business premises
Repairs and maintenance
Restoration costs (according to tenancy agreement)
Research and development
Renovation or refurbishment works (you may claim Section 14Q deduction for qualifying expenditure incurred from 16 Feb 2008 to 15 Feb 2013)
Secretarial fees
Staff remunerations (salary, bonus and allowances)
Staff training
Staff welfare/benefits
Stock obsolescence
Tax fees (service fees paid to tax agent)
Telephone
Transport (public transport and goods / commercial vehicles)
Travelling
Transport (“S” plate private passenger cars)
Wages
Water & electricity