Is it possible to legally adjust your business income to whatever number is most favorable?
Not to whatever number you'd like — but within the rules, business owners have more room to influence their taxable income than most people realize. The key is that the tools have to be used before year end, and they have to reflect real business decisions, not just paperwork.
Timing income and expenses
If you're on the cash method, you generally have some control over when income is received and when deductible expenses are paid. Delaying a December invoice into January, or paying a deductible expense before year-end instead of in January, can shift taxable income between years. This only works within reason — the IRS expects transactions to reflect actual business timing, not artificial manipulation.
Retirement plan contributions
Contributions to a SEP IRA, Solo 401(k), or traditional 401(k) reduce taxable income dollar-for-dollar (up to the applicable limit) while building retirement savings. For business owners with strong profit in a given year, this is often the single largest lever available.
Depreciation elections
Section 179 expensing and bonus depreciation let you choose, within limits, how much of an equipment or asset purchase to deduct immediately versus over several years. This is one of the more direct ways a business can adjust taxable income up or down based on purchase timing.
Accounting method and entity structure
Your overall accounting method (cash vs. accrual) and your entity structure (Sole Prop, LLC, S Corp, etc.) both affect how and when income is recognized and taxed. These aren't decisions to make every year, but getting them right for your situation has a bigger long-term effect than most single-year timing moves.
The bottom line
There's real, legal flexibility in when and how business income shows up on your return — but it has to be planned before the year closes, not reverse-engineered afterward. If you want to know what's actually available to you, that's a conversation worth having well before December.