A taxpayer whose principal business in this State is (i) manufacturing or any form of collecting, buying, assembling, or processing goods and materials within this State, or (ii) selling, distributing, or dealing in tangible personal property within this State, shall make returns and pay annually an income tax that includes its income apportioned to this State. Its income apportioned to this State is determined by multiplying the net income remaining after allocation pursuant to Sections 12-6-2220 and 12-6-2230 by a fraction, the numerator of which is the number of sales made in South Carolina, and the denominator of which is the total number of sales for the taxpayer. However, if a sales ratio does not exist, the denominator of the fraction is the number of existing ratios, and where the sales ratio exists but the payroll ratio or the property ratio does not exist, the denominator of the fraction is the number of existing ratios plus one. The sales ratios must be determined in accordance with Section 12-6-2280.