(a) The tax imposed by this chapter shall apply to the entire net income of a taxable nonresident derived from employment, trade, business, professional, or other activity for financial gain or profit performed or carried on within this state, including, but not limited to, the rental of real or personal property located within this state or for use within this state, the sale, exchange, or other disposition of tangible or intangible property having a situs in this state, the receipt of proceeds of any lottery prize awarded by the Georgia Lottery Corporation, and withdrawals of contributions to a savings trust account under Article 11 of Chapter 3 of Title 20 which are required to be included in taxable net income as provided in subparagraph (b)(10)(C) of Code Section 48-7-27.

(b) A taxable nonresident whose income is derived from employment, trade, business, professional, or other activity performed or carried on within and outside this state shall be taxed only upon the income derived from carrying on the activity within this state. The amount of taxable income may be determined by a separate accounting of the income if the commissioner is satisfied that the separate accounting reflects correctly the income fairly attributable to this state. Otherwise, the amount of taxable income shall be determined in the manner prescribed by this chapter for the allocation and apportionment of income of corporations engaged in business within and outside this state.

(c) Except as otherwise provided by law, all provisions of this chapter with respect to the definitions, determination, and computation of taxable net income of residents of this state and with respect to the assessment, levy, and collection of the tax imposed by this chapter on the net income of residents of this state shall apply equally to the taxation of the net income of taxable nonresidents.

(d) (1) A taxable nonresident shall be allowed to deduct allowable expenses, interest, taxes, losses, bad debts, depreciation, and similar business expenses when the income of the taxable nonresident is derived from:

(A) Employment, trade, business, professional, or other activity performed or carried on:

(i) Entirely within this state; or

(ii) Within and outside this state when the nonresident is permitted by the commissioner to use separate accounting;

(B) The rental of real or personal property located within this state or for use within this state;

(C) The sale, exchange, or other disposition of tangible or intangible property having a situs in this state.

(2) Expenses allowable to a taxable nonresident as provided in paragraph (1) of this subsection shall be allowable only to the extent that the expenses are attributable to the production of income allocable to and taxable by this state. As to allowable deductions essentially personal in nature, such as contributions to charitable organizations, alimony, medical expenses, the optional standard deduction, personal exemptions, and credits for dependents, the taxable nonresident shall be allowed deductions for such deductions essentially personal in nature in the ratio that the gross income allocated to this state bears to the total gross income of the taxable nonresident computed as if the taxable nonresident were a resident of this state. The commissioner may accept total federal gross income as the equivalent of total Georgia gross income for purposes of this allocation.

(e) A taxable nonresident whose income is derived from the activities specified in subsection (d) of this Code section performed or carried on within and outside this state and who is required to allocate and apportion his income in the manner of corporations engaged in business within and outside this state shall compute his net taxable income as if he were a resident of this state. The net taxable income so computed shall be apportioned in the manner of corporations engaged in business within and outside this state.