As a mortgage professional from 1998 until 2010, Christopher's answer is correct. Changing from Company A to Company B, within the same industry at the same or higher rate of pay will be a minor inconvenience. You will need proof of pay from the new job and may be required to provide a hiring letter indicating your job is secure and permanent.
If commission or bonus income becomes part of the new position, it may not be relied upon when determining your debt ratio or qualifying amount.
It is always wise to consult with your lender regarding the policy of the Bank involved in case they require anything additional.