1. "The goal of tax planning is to minimize taxes." Explain why this statement is not true. 31. Describe the business purpose, step-transaction, and substance-over-form doctrines. What types of tax planning strategies may these doctrines inhibit? 32. What is the difference between tax avoidance and tax evasion? 38. Isabel, a calendar-year taxpayer, uses the cash method of accounting for her sole proprietorship. In late December she received a $20,000 bill from her accountant for consulting services related to her small business. Isabel can pay the $20,000 bill anytime before January 30 of next year without penalty. Assume her marginal tax rate is 37 percent this year and next year, and that she can earn an after-tax rate of return of 12 percent on her investments. When should she pay the $20,000 bill-this year or next? his year or ne