A portfolio is a collection of decisions that should make sense together. Start with the job the money needs to do.
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Define the goal and constraints.
Write down the purpose, expected withdrawal date and contribution budget. Keep near-term needs visible rather than assuming every dollar can stay invested through a market decline.
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Choose a mix you understand.
Asset allocation is the division among investment types. A suitable mix depends on your circumstances, time horizon and ability to tolerate losses; there is no universal allocation.
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Check for hidden concentration.
Diversification applies both across asset types and within them. Multiple funds may overlap heavily. Spreading exposure can reduce concentration risk, but does not eliminate losses.
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Make the costs visible.
Record fund expenses, account charges and trading costs. Use the same assumptions when comparing scenarios, and remember that taxes and changing returns can affect real outcomes.
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Decide how you will review the plan.
Holdings can drift from their targets as values change. Rebalancing can involve trading or directing new contributions toward underweight holdings. Consider transaction costs and tax consequences before acting.
Write a one-page investment plan.
Use these headings: goal; time horizon; investment mix; contribution schedule; costs to monitor; review schedule; reasons you would change the plan. Leave the percentages blank until you have considered your own circumstances.
Go to the original sources
- SEC Investor.gov: asset allocation and diversification
- SEC Investor.gov: rebalancing methods and trade-offs
Guide updated October 3, 2026. The calculators illustrate assumptions and do not select a portfolio for you.