StockCharts goes to great lengths to make sure the data is accurate. Once the stock market closes, the daily quote (open, high, low, close, and volume) for each stock is audited by the exchanges. That means the people at the exchanges review all the trades for each stock, toss out any incorrect numbers, and then reissue the “official” values for open, high, low, close, and volume for that stock. To ensure we have the “official” numbers, we recollect the daily data from our data vendors several times each day after the market closes. We aim to have “official” numbers in our database for every stock's daily values.

Intraday data, however, is a different story. Exchanges do not audit intraday data values or issue corrections, nor are there any other public sources where intraday data can be cross-checked; the data simply is what it is. Intraday data is a running record of what our data feed told us the stock was trading during each minute of the trading day. That said, we still work hard to fix intraday data once it gets off the data feed and into our databases (after the markets close each day). Once the data is “ours,” we can fix any blatantly obvious problems, such as spikes and dropouts.

If you encounter a bad data point on an intraday or daily chart, we ask that you wait until the audit is complete, typically by 6:00 PM Eastern Time, before reporting the data error. This is because we cannot correct bad data while the market is open and must wait for the audit process to be completed.