Income Tax Basics
Most engineers misunderstand how income tax works. The most common misconception — "if I earn more, I might take home less because I'll be in a higher tax bracket" — is wrong, and it costs people money through bad decisions. Understanding the tax system is not optional if you want to manage your finances effectively. The US tax code is complex, but the fundamentals are straightforward.
Progressive Tax Brackets
The US federal income tax system is progressive, meaning different portions of your income are taxed at different rates. This is the single most misunderstood concept in personal finance.
2025 Federal Tax Brackets (Single Filer):
Taxable Income Rate
$0 - $11,925 10%
$11,926 - $48,475 12%
$48,476 - $103,350 22%
$103,351 - $197,300 24%
$197,301 - $250,525 32%
$250,526 - $626,350 35%
$626,351+ 37%
The key word is "taxable income," not "total income." And the key mechanism is that each bracket only applies to the income within that bracket's range.
How It Actually Works
If you earn $200,000 in taxable income:
First $11,925 taxed at 10% = $1,192.50
$11,926-$48,475 taxed at 12% = $4,386.00
$48,476-$103,350 taxed at 22% = $12,072.50
$103,351-$197,300 taxed at 24% = $22,548.00
$197,301-$200,000 taxed at 32% = $864.00
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Total federal tax: $41,063.00
Your marginal tax rate is 32% (the rate on your last dollar). Your effective tax rate is 20.5% (200,000). These are very different numbers.
Why This Matters
The progressive system means earning more money never results in less take-home pay. Moving into a higher bracket only affects the dollars in that bracket, not your entire income.
Common mistake:
"I don't want a raise from $103,000 to $110,000 because
I'll jump from 22% to 24% and pay more in taxes."
Reality:
The 24% rate only applies to the $6,650 above $103,350.
Additional tax: $6,650 * 24% = $1,596
You keep: $6,650 - $1,596 = $5,054
You take home an additional $5,054. Always accept the raise.
Marginal vs Effective Tax Rate
These two numbers tell you different things, and you need both:
Marginal rate: The tax rate on your NEXT dollar of income.
Used for: deciding whether to take on additional
income, evaluating the value of deductions.
Effective rate: Your total tax divided by total income.
Used for: understanding your actual tax burden,
budgeting, comparing tax situations.
Example ($200k single filer, 2025):
Marginal rate: 32%
Effective rate: 20.5%
Practical use:
"Should I do $5k of freelance work?"
-> Look at marginal rate: 32% federal + 9.3% CA state
+ 15.3% self-employment tax = ~57% marginal rate on
that freelance income. You keep $2,150 of that $5k.
"What percentage of my salary goes to taxes overall?"
-> Look at effective rate: ~30-35% all-in (federal +
state + FICA).
Pre-Tax vs Post-Tax Deductions
Some deductions reduce your taxable income before tax is calculated. Others come out of after-tax dollars. The difference matters enormously.
Pre-tax deductions (reduce your taxable income):
Traditional 401k contributions: up to $23,500/year
HSA contributions: up to $4,150/year (individual)
Health insurance premiums: varies
FSA contributions: up to $3,300/year
Traditional IRA: up to $7,000/year (if eligible)
Post-tax deductions (no tax reduction):
Roth 401k contributions
Roth IRA contributions
After-tax investment contributions
Example impact of pre-tax deductions:
Gross income: $200,000
401k contribution: -$23,500
HSA contribution: -$4,150
Health premiums: -$3,600
Taxable income: $168,750
Tax on $200,000: $41,063
Tax on $168,750: $33,050
Tax savings: $8,013/year
That $8,013 doesn't disappear — you've redirected it into retirement and health savings instead of the IRS. The money is still yours, just in tax-advantaged accounts.
W-2 vs 1099 Income
Most engineers are W-2 employees. Some do contracting or freelance work on the side and receive 1099 income. The tax treatment is significantly different.
W-2 (Employee):
- Employer withholds federal/state tax from each paycheck
- Employer pays half of FICA (7.65%)
- You pay the other half (7.65%)
- Total FICA: 15.3%, split evenly
1099 (Independent Contractor):
- No withholding (you're responsible for paying taxes)
- You pay BOTH halves of FICA (15.3% self-employment tax)
- You must pay quarterly estimated taxes
- Penalties for underpayment
Same $10,000 of income:
W-2: You pay $765 FICA + income tax
1099: You pay $1,530 FICA + income tax (double the FICA)
This is why a 150/hour salary. After accounting for self-employment tax, no benefits, no PTO, no 401k match, and no employer-paid insurance, you need roughly 150/hour as an employee.
State Tax Differences
State income tax varies dramatically and can be the single largest variable in your tax situation:
No state income tax:
Texas, Florida, Washington, Nevada, Wyoming,
South Dakota, Alaska, Tennessee, New Hampshire*
(*NH taxes dividends/interest only)
High state income tax:
California: up to 13.3%
New York: up to 10.9% (+ NYC tax up to 3.876%)
Oregon: up to 9.9%
Minnesota: up to 9.85%
New Jersey: up to 10.75%
Impact on a $250k salary:
Living in Texas: $0 state income tax
Living in California: ~$17,000 state income tax
Living in NYC: ~$20,000 state + city income tax
Annual difference TX vs NYC: ~$20,000
Over 10 years: ~$200,000 (not counting investment growth)
This doesn't mean you should move to Texas. Cost of living, career opportunities, quality of life, and personal preferences all matter. But you should be aware of the financial impact and factor it into compensation comparisons.
Remote Work Across State Lines
Remote work has created tax complexity. The rules vary by state and are still evolving:
Scenario: You work for a California company but live in Texas.
General rule: You pay taxes where you physically work.
-> If you work from Texas, you owe Texas tax (zero).
-> You don't owe California tax on that income.
Exceptions:
- "Convenience of the employer" states (New York):
If your employer is in NY and you work remotely for
your own convenience (not the company's requirement),
NY may still tax your income.
- Temporary work in another state:
If you travel to the company's office in CA for 2 weeks,
you may owe CA tax on that 2 weeks of income.
- Multi-state residency:
If you split time between states, you may owe taxes
in multiple states with credits to avoid double taxation.
Best practice:
- Know your company's remote work tax policy
- Track days worked in each state
- Consult a tax professional if you work across state lines
The Standard Deduction
The standard deduction is an amount you can subtract from your gross income before taxes are calculated. Most engineers should take the standard deduction rather than itemizing.
2025 Standard Deduction:
Single: $15,000
Married Filing Jointly: $30,000
What this means:
Gross income: $200,000
Standard deduction: -$15,000
Taxable income: $185,000
Itemizing makes sense only if your deductions exceed $15,000:
State/local tax (SALT): capped at $10,000
Mortgage interest: varies
Charitable donations: varies
Medical expenses: above 7.5% of AGI
For most single engineers renting an apartment:
SALT cap: $10,000
Other: minimal
Total: ~$10,000 (less than $15,000 standard deduction)
-> Take the standard deduction.
For married homeowners with a mortgage:
SALT cap: $10,000
Mortgage interest: $8,000-$20,000
Charitable: $2,000-$5,000
Total: $20,000-$35,000 (may exceed $30,000)
-> Itemizing may be beneficial. Run the numbers.
FICA Taxes
FICA (Federal Insurance Contributions Act) taxes fund Social Security and Medicare. They're separate from income tax and are often overlooked in take-home pay calculations.
FICA rates (employee portion):
Social Security: 6.2% on income up to $176,100 (2025)
Medicare: 1.45% on all income
Additional Medicare: 0.9% on income above $200,000 (single)
On a $250k salary:
Social Security: $176,100 * 6.2% = $10,918
Medicare: $250,000 * 1.45% = $3,625
Additional Medicare: $50,000 * 0.9% = $450
Total FICA: $14,993
FICA is not deductible. It comes off the top.
Your employer pays an equal amount on your behalf.
Common Pitfalls
- Thinking a raise can put you in a worse position. Progressive taxation means more income always means more take-home pay. The higher rate applies only to the income in that bracket.
- Confusing marginal and effective rates. Your marginal rate might be 32% but your effective rate is 20%. Use the right number for the right purpose.
- Not maxing pre-tax deductions. Skipping the 401k or HSA means paying thousands more in taxes for no benefit. At a 32% marginal rate, every 320.
- Ignoring state tax in job comparisons. A 230k offer in Seattle have very similar take-home pay. The $20k "pay cut" is largely offset by zero state income tax.
- Not understanding 1099 tax obligations. Freelance income is taxed roughly 15% more than W-2 income due to self-employment tax. Price your freelance rate accordingly.
- Assuming your withholding is correct. Many engineers get large refunds (meaning they over-withheld) or owe money at filing (meaning they under-withheld). Adjust your W-4 to get it close to zero.
Key Takeaways
- The US tax system is progressive. Each bracket only taxes the income within its range. Higher income always means higher take-home pay.
- Know both your marginal rate (for incremental decisions) and your effective rate (for budgeting).
- Pre-tax deductions (401k, HSA) reduce your tax bill dollar-for-dollar at your marginal rate. Max them out.
- State tax is a major variable: 17k+ in California on a $250k salary. Factor this into job comparisons.
- W-2 and 1099 income are taxed very differently. A 150/hour salary.
- Most single renters should take the standard deduction. Run the numbers if you're a homeowner or make large charitable contributions.