A Lean Six Sigma project team reduced the number of paperwork errors in the purchase order placement process.

A Lean Six Sigma project team reduced the number of paperwork errors in the purchase order placement process. I would like to monitor the process for the number of defectives to ensure that the process does not encounter more errors. The data is being tracked daily by looking at all the applications processed each day and counting how many are defective. Which control chart should I use?