Yes, a stock can have a negative pricetoearnings ratio (P/E), but it is very unlikely that you will ever see it reported. Although negative P/E ratios are mathematically possible, they generally aren't accepted in the financial community and are considered to be invalid or just not applicable. We'll explain why this is.
The priceearnings ratio is arguably the most popular fundamental factor used by investors who try to determine the attractiveness of an asset's current value and, more importantly, whether the current price level makes for a good buying opportunity. The ratio is calculated by dividing a financial asset's current share price by its pershare earnings. Generally speaking, a low P/E value suggests that an investor needs to pay a low amount for each dollar of earnings made by the company. This could be used by investors as a sign that the given asset is undervalued and a potentially good investment at current levels. Conversely, a relatively high P/E value is used to suggest that investors will need to pay a high amount for the company's earnings, which can then be used to suggest that the asset is relatively expensive and that it may be a good idea to wait for a better entry.
Mathematically, there are only two ways for a ratio of this form to have a negative value:
 The numerator falls below zero
 The denominator falls below zero.
In the case of the P/E ratio, it is impossible for the numerator to fall below zero because this represents the price of the asset. However, the denominator, which is equal to the earnings of the company, can become negative. EPS values below zero mean that the company is losing money and is the reason why it is possible to have a negative P/E ratio.
Negative EPS numbers are usually reported as "not applicable" for quarters in which a company reported a loss. Investors buying a company with a negative P/E should be aware that they are buying a share of a company that has been losing money per share of its stock.
For further reading, see our tutorials on Understanding the P/E Ratio and Ratio Analysis.

How can the pricetoearnings (P/E) ratio mislead investors?
A low P/E ratio doesn't automatically mean a stock is undervalued, just like a high P/E ratio doesn't necessarily mean it ... Read Answer >> 
What does it mean when "N/A" appears for a company's P/E ratio?
A "N/A" reported in a stock's pricetoearnings ratio (P/E), can mean one of two things. The first, and simplest, would be ... Read Answer >> 
What does the forward p/e indicate about a company?
Explore the forward price to earnings ratio and learn its significance and how it compares to the traditional price to earnings ... Read Answer >> 
What does it mean if a bond has a zero coupon rate?
Learn what the average range for the price to earnings (P/E) ratio in the electronics sector is and which factors influence ... Read Answer >> 
Stocks with high P/E ratios can be overpriced. Is a stock with a lower P/E always ...
The short answer? No. The long answer? It depends.The pricetoearnings ratio (P/E ratio) is calculated as a stock's current ... Read Answer >> 
What is the difference between forward p/e and trailing p/e?
Understand the difference between the trailing P/E ratio, which is the standard pricetoearnings calculation, and the forward ... Read Answer >>

Investing
Beware False Signals From The P/E Ratio
The P/E ratio is a simple tool for evaluating a company, but no one ratio can tell the whole story. 
Investing
Can Investors Trust The P/E Ratio?
The P/E ratio is one of the most popular stock market ratios, but it has some serious flaws that investors should know about. 
Investing
How Do I Calculate the PriceEarnings Ratio?
If Apple is trading at $108.73 per share, and its trailing twelve months' EPS is $6.45, calculate the P/E ratio as... 
Investing
How To Use The P/E Ratio And PEG To Tell A Stock's Future
While the pricetoearnings ratio is commonly used for assessing stock prices, the price/earningstogrowth ratio offers forecasting advantages that investors need to know. 
Investing
Explaining Forward PricetoEarnings Ratio
The estimated P/E of a company is often used to compare current earnings to estimated future earnings. 
Investing
5 MustHave Metrics For Value Investors
These quickanddirty ratios will help you find the most undervalued stocks on the market. 
Investing
The 4 Basic Elements of Stock Value
Investors use these four measures to determine a stock's worth. Find out how to use them. 
Investing
Understanding The P/E Ratio
Learn what the price/earnings ratio really means and how you should use it to value companies.

PriceEarnings Ratio  P/E Ratio
The PricetoEarnings Ratio or P/E ratio is a ratio for valuing ... 
P/E 30 Ratio
The pricetoearnings (P/E) ratio is the valuation ratio of a ... 
Forward Price To Earnings  Forward P/E
A measure of the pricetoearnings ratio (P/E) using forecasted ... 
Ratio Analysis
A ratio analysis is a quantitative analysis of information contained ... 
Trailing PriceToEarnings  Trailing P/E
The sum of a company's pricetoearnings, calculated by taking ... 
Price/Earnings To Growth  PEG Ratio
Price/Earnings to Growth (PEG) is a stock's price to earnings ...