What it means
Total income includes wages, self-employment profit, interest, dividends, taxable retirement withdrawals, rental profit and most other receipts the tax rules recognise. From that total, a defined list of adjustments is subtracted, sometimes called above the line deductions because they sit above the AGI line on the return.
Typical examples are contributions to certain retirement accounts, health savings account contributions, student loan interest and the deductible portion of self-employment tax. AGI matters more than most people expect because it acts as the gatekeeper for other tax benefits.
Credits and allowances often phase out above particular AGI levels, so two households with identical gross income can face different outcomes depending on how much they contributed to a retirement or health savings account. The order of the calculation is the part that trips people up.
Gross income minus above the line adjustments gives AGI, and only then are the standard deduction or itemised deductions subtracted to arrive at taxable income, which is what the tax rates apply to. Because AGI sits above those later deductions, a dollar of above the line contribution can be worth more than a dollar of itemised deduction.
It reduces the tax due and simultaneously improves eligibility for anything tested against AGI, which is why advisers often prioritise those contributions first. You will also meet modified adjusted gross income, or MAGI, which is AGI with certain items added back for the purposes of one particular test.
Frustratingly, the definition of MAGI differs depending on which relief is being tested, so it must be recalculated for each one rather than treated as a single number. For a business audience, AGI shows up whenever an owner's personal position interacts with company decisions, such as choosing between salary and dividends, timing a bonus, or deciding how much to put into a retirement plan before the year ends.
A finance director who understands where the thresholds sit can often improve an owner's net position without increasing company cost.
In practice
Real-world examples.
Example
A consultant earning $140,000 discovers that a tax credit she wants phases out at an AGI of $130,000. Increasing her retirement contribution by $12,000 before the year end brings her AGI to $128,000 and restores the credit as well as reducing the tax on the contribution itself.
Example
A small company owner is deciding between a $20,000 bonus in December and the same amount in January. Because a bonus this year would push his AGI past a threshold that reduces a family benefit, the payment is deferred and the company's cost is unchanged.
Example
A mortgage adviser asks a self-employed applicant for her AGI over two years rather than her turnover. The figures show $78,000 and $84,000 after business deductions, and the lender sizes the loan against those rather than the much larger gross billings.
Think of it
“AGI is income after certain deductions-key number for tax calculations.
Formula
Calculation
Adjusted gross income = total gross income - above the line adjustments
Consider an employee with a salary of $95,000, taxable dividends from an investment account of $12,000 and bank interest of $500. Total gross income = $95,000 + $12,000 + $500 = $107,500.
During the year she contributed $3,500 to a health savings account and $8,000 to a traditional individual retirement account, both of which qualify as above the line adjustments. Total adjustments = $3,500 + $8,000 = $11,500.
Adjusted gross income = $107,500 - $11,500 = $96,000. If she then claims a standard deduction of $15,000, her taxable income is $96,000 - $15,000 = $81,000, and it is that final figure, not the AGI, to which the tax rates are applied.Case study
Seen in the real world.
The following is an illustrative and fictional scenario. Larkfield Dental, an invented two partner practice, paid each partner a salary of $118,000 plus a discretionary year end bonus, and the partners had never looked at how those payments interacted with their personal tax positions. In one year the bonus was set at $22,000 each purely because that was what the practice could afford.
The practice's accountant modelled the effect and found that the bonus pushed both partners' AGI above a threshold where a relief they had been claiming began to phase out, so a meaningful slice of the extra pay was absorbed by lost benefits. Redirecting $14,000 of each bonus into the practice retirement plan kept AGI below the threshold while leaving total remuneration unchanged.
In this fictional account the change cost Larkfield nothing, since the money left the practice either way, but it improved each partner's net position by several thousand dollars. The partners now review the split between bonus and retirement contribution every November, before the amounts are fixed.
Watch out
Common mistakes.
- Confusing AGI with taxable income, when the standard or itemised deduction is still to be subtracted after the AGI line.
- Assuming every deduction reduces AGI, when itemised deductions such as mortgage interest and charitable gifts sit below the line and do not.
- Treating modified adjusted gross income as one fixed figure, when the add-backs differ depending on which relief is being tested.
Questions
People also ask.
Why does AGI matter if it is not the figure I am taxed on?
Because eligibility for a long list of credits, allowances and thresholds is tested against AGI rather than against taxable income.
Do business expenses reduce AGI for a self-employed person?
Yes, legitimate business expenses reduce the profit that enters total income, so they lower AGI before any above the line adjustments are applied.
Can I reduce my AGI after the tax year has ended?
Sometimes, because certain retirement and health savings contributions can be made up to the filing deadline and still counted for the previous year.
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