A stock has doubled. What should you review before selling or holding?

Separate the gain from its explanation#

Check the dates, currency and corporate actions behind the price comparison. A split-adjusted price change is not the same as a total return including dividends, and neither is necessarily your realised return after costs and taxes.

Then examine the company evidence. Did earnings grow, financial risks fall or expectations rise? There may be several contributors, and public evidence may not identify exactly how much each caused the price change.

Ask how much the valuation changed#

Consider a fictional stock rising from $20 to $40. If earnings per share also rose from $1 to $2, the P/E remained 20. If earnings stayed at $1, the P/E rose from 20 to 40.

The same 100% price increase therefore describes different changes in valuation. Neither scenario alone determines what comes next. You still need to assess whether earnings are repeatable and what future progress the new price assumes.

Use the P/E guide to examine the denominator and distinguish historical earnings from forecasts.

Recheck the business rather than celebrating the chart#

Read the latest results and material announcements. Compare customer demand, margins, cash generation, debt and share count with the original case.

A good price outcome does not prove every assumption in your thesis was correct. A business can outperform for a reason you did not anticipate, or its shares can rise while an important risk remains unresolved. Keep the result and the quality of the reasoning separate.

Measure the new concentration#

Suppose a $10,000 holding in a $100,000 portfolio doubles while everything else remains unchanged. The holding becomes $20,000 and the portfolio $110,000. Its weight rises from 10% to approximately 18.182%, not 20%.

This hypothetical calculation ignores other movements, contributions and distributions. It shows why a successful position can change portfolio exposure without another purchase. Review shared industry or company exposure in funds as well as direct holdings.

FINRA's concentration guidance explains the risks of relying too heavily on one investment or common exposure. It does not prescribe one correct weight for every investor.

Consider the decision from today#

Your purchase price matters to records and potentially tax, but it does not determine today's business value. Nor does a round-number gain create a special economic deadline.

Compare the current thesis with plausible weaker outcomes and your own need for liquidity. Tax consequences depend on your jurisdiction and circumstances; obtain appropriate guidance rather than applying a generic internet rule.

Record what would cause you to reassess again. That may be an operating change, financing event or a valuation assumption becoming difficult to support. A disciplined review should remain useful whether the next price move is favourable or not.