Which of the following best describes an 'allowable expense'?

An 'allowable expense' is best described as costs incurred that can be deducted to reduce taxable profit. This means that when a business incurs expenses that are necessary for the operation of the business and meet specific criteria set by tax laws, these expenses can be subtracted from the total income, thereby lowering the taxable profit and, subsequently, the tax liability.

Allowable expenses typically include costs such as salaries, utilities, rent, and office supplies, as they are directly related to generating income. This concept is essential for businesses as it helps them manage their taxable income effectively, allowing them to invest more back into the business or pay dividends, depending on their financial strategy.

The other options do not accurately capture the essence of allowable expenses. Personal expenses are not deductible for business tax purposes, thus would not qualify. Not all costs related to capital assets are fully deductible in the year they are incurred; often, they are capitalized and written off over time through depreciation. Lastly, expenses linked only to promotional activities would not encompass the broader range of deductible business costs that are categorized as allowable expenses in tax law.