Final answer:
Phasma will likely be taxed on the value of the cruise tickets based on the principle of constructive receipt, since she earned the reward and directed its use, even though her parents were the recipients of the tickets.
Step-by-step explanation:
The principle that will determine whether Phasma or her parents are taxed on the value of the cruise tickets is related to the tax concept called constructive receipt. Under the cash-basis taxpayer rules, income is generally taxable to the person who earns it when it is actually or constructively received.
In Phasma's case, even though she directed the benefit to her parents, she earned the reward and had control over its disposition; therefore, it is likely that the Internal Revenue Service (IRS) would consider Phasma to have constructively received the income. This means that Phasma would be taxed on the value of the cruise. However, for a definitive answer, it would be necessary to consult the IRS guidelines or a tax professional.
The principles of taxation, including the benefit principle and the ability-to-pay principle, offer different viewpoints on how taxes should be levied. The benefit principle suggests that those who benefit from services should pay in proportion to the benefits received, while the ability-to-pay principle argues that taxes should be based on an individual's financial capacity.