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 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 >> 
How can I find the P/E ratio on an ETF's underlying index?
Learn how analysts and investors can determine the pricetoearnings ratio for the underlying index of an exchangetraded ... Read Answer >> 
What is the average pricetoearnings ratio in the automotive sector?
Learn the average pricetoearnings ratio for the automotive sector and how it is used to evaluate a company’s potential ... Read Answer >> 
What is the average pricetoearnings ratio in the food and beverage sector?
Learn what the average pricetoearnings ratio is in the food and beverage sector and why other measures such as median should ... 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
Getting On The Right Side Of The P/E Ratio Trend
Buying at the right time is crucial, but how do we know when that is? 
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
Comparing the P/E, EPS And Earnings Yield
Here are three ratios that help investors value stock returns. 
Investing
Is Stock With a Lower P/E Always A Better Choice?
Is a stock with a lower P/E always a better investment than a stock with a higher one? The short answer is no, but it depends on a few things. 
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.

PriceEarnings Ratio  P/E Ratio
The PricetoEarnings Ratio or P/E ratio is a ratio for valuing ... 
Ratio Analysis
A ratio analysis is a quantitative analysis of information contained ... 
P/E 10 Ratio
A valuation measure, generally applied to broad equity indices, ... 
Key Ratio
A mathematical ratio that illustrates and summarizes the current ... 
Valuation
The process of determining the current worth of an asset or company. ... 
Franchise Factor
The measurement of the impact on a company's priceearnings (P/E) ...