There is a distinction between base pay and gross pay. Gross pay or wages represent what the employee has earned, including regular wages, overtime wages, bonuses, commissions, paid-time-off. Not all pay codes typically affect base pay, such as Overtime, Doubletime, Tripletime or other premium pay wages. Expense Reimbursements are gross pay but are excluded from base pay. Not all pay codes affect 401(k) and 403(b), as determined by employer specific policies.
Wage garnishments are typically expressed as a percent of Disposable Wages. Disposable Wages is calculated as Taxable Wages - Tax Withholdings.