Most tax savings for regular earners come from three decisions: which retirement accounts to use, when to realise gains, and whether to itemize. Everything else is rounding error by comparison.
How tax brackets work
Progressive tax systems tax different slices of income at different rates. Being 'in the 24% bracket' doesn't mean paying 24% on all your income — only on the portion above the previous bracket's threshold.
This is why 'a raise will push me into a higher bracket' isn't a real concern for the raise itself. Only the marginal dollars above the threshold are taxed at the higher rate; everything below stays where it was.
Marginal vs effective rate
The marginal rate is what your next dollar of income (or deduction) is worth. The effective rate is your total tax divided by total income — always lower than the marginal rate in a progressive system.
Understand your marginal rate to size decisions like Roth vs Traditional contributions, whether to take a bonus this year or next, and how much a charitable deduction is actually worth.
Tax-advantaged accounts
- 401(k) / 403(b): pre-tax now, taxed on withdrawal.
- Roth 401(k) / Roth IRA: taxed now, tax-free growth and withdrawals in retirement.
- Traditional IRA: pre-tax if under income limits, taxed on withdrawal.
- HSA: triple tax advantage (deductible in, tax-free growth, tax-free out for medical).
- 529: state deduction possible, tax-free growth for education expenses.
Capital gains rules
Short-term capital gains (assets held one year or less in the US) are taxed as ordinary income. Long-term capital gains get preferential rates. That's a huge incentive to hold investments at least a year past purchase before selling.
Losses can offset gains and, in the US, up to $3,000 of ordinary income per year. Extra losses carry forward indefinitely. This is the basis for tax-loss harvesting.
Standard vs itemized
You take whichever is higher: the flat standard deduction or the sum of itemized deductions (mortgage interest, state and local taxes, charitable giving, medical over a threshold). Since the 2017 US tax law raised the standard deduction significantly, most households now take it.
Year-round planning
- Adjust withholding once a year to avoid big refunds (which are interest-free loans to the government).
- Front-load retirement contributions to maximise growth time.
- Bunch deductions (e.g. charitable giving) into one year to itemize occasionally.
- Review at year-end whether to realise gains, harvest losses, or make Roth conversions.
Frequently asked questions
How do tax brackets work?
Different slices of your income are taxed at different rates. Only the portion above each threshold pays the higher rate — not your entire income.
What is the difference between marginal and effective tax rate?
Marginal is the rate on your next dollar. Effective is total tax divided by total income. Effective is always lower than marginal in a progressive system.
Should I max my 401(k) or IRA first?
Contribute to a 401(k) up to any employer match first, then max an IRA (especially Roth if eligible), then return to the 401(k) for the remainder.
What is tax-loss harvesting?
Selling investments at a loss to offset realised gains, reducing tax owed. You immediately buy a similar-but-not-identical fund to stay invested. Watch out for the 30-day wash-sale rule.
Put this into practice
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