n addition to personal and additional exemptions and deductions for health insurance premiums, individuals who earn income from a trade, business or the practice of a profession may deduct expenses incurred in connection with their trade, business or profession subject to Philippine income tax. These expenses include ordinary and necessary business or professional expenses, interest expense, taxes, losses, bad debts, depreciation, charitable contributions, contributions to a pension trust, and research and development. Alternatively, such taxable individual (except a nonresident alien not engaged in trade or business) may elect the optional standard deduction (OSD) of 40% of gross income instead of the itemized deductions. A taxpayer must signify his or her intention to claim the OSD in the annual tax return; otherwise, the taxpayer is deemed to have claimed the itemized deductions. After the election to claim the OSD is indicated in the return, it is irrevocable for the tax year for which the return is filed.