Identify the tax issue or issues suggested by the following situations, and state each issue in the form of a question.
Wiggins Corporation is a calendar year taxpayer. For the past nine years, its taxable income has been stable, averaging $2 million per year. Through November of this year, its taxable income was $1.81 million. In April, June, and September, Wiggins made a $175,000 installment payment of tax. In December, it recognized a $5 million gain on the sale of investment land.