Which of the following is NOT a factor in determining capital gains on a property sale?

When determining capital gains on a property sale, the calculation primarily revolves around the difference between the selling price and the adjusted basis of the property. The original purchase price is a foundational element because it establishes the property's basis. Selling expenses are also relevant as they reduce the amount of the gain by allowing sellers to deduct costs associated with selling, such as real estate commissions and closing costs. The length of ownership affects certain tax considerations, such as whether a gain qualifies for long-term capital gains tax rates or if it qualifies for specific exemptions.

In contrast, the annual income of the seller does not play a role in calculating capital gains. Capital gains tax is based on the profit made from the sale of the property rather than the income level of the seller. Therefore, it is not a factor in the capital gains calculation, making it the correct answer in this context.