What happens if you discover that you have not deducted enough CPP, EI or QPIP from an employees pay-cheque? Often time this error is uncovered when the CRA sends you a Notice of Assessment or you may uncover the error yourself. The contributions can be made up by deducting these under contributions on future pay-cheques to the employee. This can be done for outstanding contributions that are not more than 12 months old.
For further information, see the CRA website here.