As U.S. equities stage a strong rebound this week, a historical pattern is quietly approaching—April 15th, the U.S. tax filing deadline, has seasonally been the worst-performing day on average for the S&P 500 throughout the year.
Historical data shows that since 1990, the median daily return of the S&P 500 around April 15th ranks at the bottom among all trading days. This is widely attributed to investors being forced to liquidate assets to cover tax payments before the deadline. Although the Federal Reserve actively manages market liquidity around the tax deadline, historical data indicates that, on average, this liquidity injection has been insufficient to prevent stock market declines.
Overall market sentiment this week has been optimistic, with the S&P 500's overnight closing price significantly higher than levels seen before the recent escalation of geopolitical tensions. Investors appear to be putting recent risk events behind them. However, seasonal patterns suggest that short-term downward pressure remains, warranting investor caution.
Tax Deadline Weighs on Stocks: A Clear Historical Pattern Looking back at data since 1990, the two dates with the lowest median returns for the S&P 500, measured across all trading days, are April 15th and June 7th.
The negative effect of April 15th has a relatively straightforward explanation: it is the annual deadline for U.S. individual income tax returns, forcing many investors to sell holdings to raise funds for tax payments, thereby creating concentrated selling pressure. The pattern for June 7th is more puzzling. Although there is a minor tax-related date in mid-June, the reason selling pressure appears ahead of this date lacks a clear explanation. It is important to note that these dates are not fixed trading days; if they fall on a non-trading day, the effect shifts, leading to some variability in the actual impact date. Fed Intervenes to Manage Liquidity, With Limited Effect Around the tax filing deadline, the Federal Reserve proactively manages liquidity. Typically, before the April deadline, the Treasury's account balance at the Fed decreases, indicating liquidity is injected into the market. After the deadline, as tax payments flow into government accounts, this balance rises again.
However, historical seasonal data shows that, on average, this preemptive liquidity injection has not been enough to counteract stock market downward pressure. In other words, even with the Fed's buffering operations, stock market weakness around the tax deadline remains a statistically significant pattern. Short-Term Risks Coexist with Rebound Potential Beyond seasonal patterns, the current market faces more complex bullish and bearish forces.
On the bearish side, even if this year repeats the historical pattern, the impact may be limited to the short term. Historical data also indicates that after April 15th, the S&P 500 has, on average, recorded positive returns for the remainder of April, suggesting seasonal pressure is relatively contained. However, May is generally one of the months with the lowest average returns for the year, and the market adage "Sell in May" could become a self-fulfilling prophecy to some extent. On the bullish side, current pessimism among both retail and institutional investors is at elevated levels. This consensus bearishness could itself become a catalyst for a rebound—short covering or the rebuilding of risk exposure could potentially drive stocks higher in the coming weeks. This week's rally might be the beginning of this process. Seasonal patterns ultimately serve only as reference points and must be adjusted based on the current market environment. For investors, maintaining caution around the tax deadline while watching for potential short-covering rallies ahead may be a more balanced strategy.
