Discretionary income is the money left over after you’ve paid taxes and covered the necessary costs of living, such as housing, food, utilities, transportation, and minimum debt payments. It’s the portion of your earnings you can actually choose how to use, whether that means saving, investing, or spending on things you want rather than things you need. The term also has a stricter legal meaning under federal student loan repayment, where it’s calculated from your adjusted gross income and a set poverty threshold rather than your real household bills.
Discretionary Income vs. Disposable Income
The two terms sound similar and often get swapped, but they measure different things. Disposable income is your take-home pay: gross earnings minus mandatory deductions like federal and state income taxes, Social Security, and Medicare. If your paycheck lands at $4,500 after withholdings, that $4,500 is disposable income.
Discretionary income takes one more step. From that disposable figure, you subtract the necessary costs of running your life. What remains is money you have genuine choice over.
The gap between the two can flip the picture of who is better off. Someone bringing home $7,000 a month with $5,500 in fixed costs has $1,500 in discretionary income. Someone bringing home $4,000 with only $2,000 in fixed costs has $2,000 in discretionary income. The lower earner has more financial breathing room.
How to Calculate Discretionary Income
The formula is simple in outline: start with gross income, subtract taxes and mandatory deductions to get disposable income, then subtract necessary living expenses. The second subtraction is where judgment enters, because “necessary” isn’t a fixed number.
A worked example for someone earning $72,000 a year:
- Gross monthly income: $6,000
- Taxes and mandatory deductions: −$1,500 (federal and state income tax, Social Security, Medicare)
- Disposable income: $4,500
- Necessary expenses: −$2,900 (rent $1,400, utilities $250, groceries $400, health insurance $300, minimum debt payments $350, transportation $200)
- Discretionary income: $1,600
That $1,600 is available for dining out, entertainment, extra retirement contributions, or building savings. If the number comes out negative, essentials alone are costing more than you earn, and something in the income or expense side has to change.
Court-Ordered Payments
Child support and alimony sit in a gray area. Legally you have to pay them, which makes them non-negotiable in the same practical sense as taxes, and most financial planners treat them as necessary expenses in a personal budget. For tax and student-loan purposes, though, what counts is whether the payment reduces your adjusted gross income. Child support never does. Alimony under agreements executed after 2018 doesn’t either, since it’s no longer tax-deductible for the payer.1Internal Revenue Service. Alimony and Separate Maintenance
Pre-Tax Retirement and Health Contributions
Traditional 401(k) and HSA contributions come out of your paycheck before taxes, which lowers your AGI. For a monthly budget, these are optional; you could stop them at any time. But for anything that starts from AGI, including federal student loan payments, every dollar you put into a traditional 401(k) or HSA reduces the discretionary income figure the calculation lands on. Roth contributions don’t have this effect, because they’re made with after-tax dollars.
What Counts as a Necessary Expense
For your own budget, you decide where the line runs. When a government agency needs to draw that line, it uses published standards. The IRS maintains National Standards and Local Standards that set allowable amounts for food, clothing, housing, utilities, and transportation, keyed to household size and geography.2Internal Revenue Service. Collection Financial Standards
Under IRS collection standards, you’re generally allowed the lower of what you actually spend or the local standard. The national food allowance is $497 per month for one person and $1,255 for a household of four.3Internal Revenue Service. National Standards – Food, Clothing and Other Items Housing and utility allowances vary by county to reflect the difference between, say, rural and major-metro costs.
Categories that generally count as necessary include:
- Housing: rent or mortgage payments, property taxes, homeowners or renters insurance
- Utilities: electricity, water, heat, garbage collection, basic phone and internet
- Food: reasonable grocery costs for the household size
- Transportation: vehicle maintenance and fuel, or public transit
- Insurance: health insurance and required auto insurance
- Minimum debt payments on existing loans and credit accounts
Some line items are clearly one or the other. Basic internet for work is necessary; a premium streaming bundle isn’t. A used sedan to reach your job is necessary; a luxury car lease that triples the payment is discretionary spending wearing a transportation label.
The Student Loan Formula
If you have federal student loans, “discretionary income” has its own legal definition that ignores your actual rent and groceries. Income-driven repayment plans calculate it from your AGI and the federal poverty guideline for your family size.
Under Income-Based Repayment (IBR) and Pay As You Earn (PAYE), discretionary income equals your AGI minus 150% of the poverty guideline.4GovInfo. 20 USC 1098e – Income-Based Repayment Under Income-Contingent Repayment (ICR), only 100% of the guideline is subtracted, so the number comes out higher.5Consumer Financial Protection Bureau. Data Point – Borrower Experiences on Income-Driven Repayment
The 2026 poverty guideline in the 48 contiguous states is $15,960 for a single person, $21,640 for two, $27,320 for three, and $33,000 for four.6Federal Register. Annual Update of the HHS Poverty Guidelines7U.S. Department of Health and Human Services. 2026 Poverty Guidelines – 48 Contiguous States
For a single borrower with an AGI of $45,000, the IBR or PAYE calculation runs as follows:
- 150% of the poverty guideline: $15,960 × 1.5 = $23,940
- Discretionary income: $45,000 − $23,940 = $21,060
The monthly payment is a percentage of that figure. IBR charges 10% for borrowers who first took out loans after July 1, 2014, and 15% for earlier borrowers. PAYE charges 10%.8Federal Student Aid. Income-Driven Repayment Plans For a new IBR borrower in this example, that’s about $175 a month ($21,060 × 10% ÷ 12).
Because the formula starts from AGI, anything that lowers AGI lowers the payment. Traditional 401(k) contributions, HSA contributions, and above-the-line deductions like student loan interest all pull the number down. Roth contributions don’t. On an income-driven plan, choosing between traditional and Roth accounts is partly a student loan decision.
The currently available income-driven plans are IBR, PAYE, and ICR.8Federal Student Aid. Income-Driven Repayment Plans The SAVE plan, which used a more generous 225% poverty threshold, is no longer open to new enrollment.
Discretionary Income in the Bankruptcy Means Test
Bankruptcy courts use a similar idea under a different name. The Chapter 7 means test asks whether a debtor has enough surplus income to fund a repayment plan; if so, filing under Chapter 7 is presumed abusive. The court measures monthly income and subtracts allowable expenses taken from the IRS National and Local Standards.9Office of the Law Revision Counsel. 11 USC 707 – Dismissal of a Case or Conversion to a Case Under Chapter 11 or 13
You can’t claim whatever you actually spend. Food, clothing, housing, and transportation allowances are capped by IRS figures, with housing and utility limits keyed to the county.10U.S. Department of Justice. IRS National Standards for Allowable Living Expenses The court may add 5% above the food and clothing standard when the debtor shows it’s reasonable. Health and disability insurance are counted. Payments on existing debts generally are not. If the resulting surplus over 60 months clears certain thresholds, the court presumes the debtor can fund a Chapter 13 plan rather than discharge debts through Chapter 7.
Why the Number Matters
Lenders use discretionary income to gauge whether you can carry another payment. A high paycheck means little if fixed costs consume most of it, so the money left after essentials is a better read on true borrowing capacity than gross income alone.
The same logic applies to your own planning. Tracking discretionary income over several months surfaces patterns that gross pay hides. You can earn $80,000 and still struggle to save if your necessary costs are heavy, or earn $50,000 and save well because your cost structure is lean. For building wealth, what matters isn’t what you earn. It’s what’s left after the bills you can’t skip.