Budgetary control is financial jargon for managing income and expenditure. In practice it means regularly comparing actual income or expenditure to planned income or expenditure to identify whether corrective action is required.
For example, most University institutions are given annual Chest allocation budgets for certain staff costs. By regularly comparing actual expenditure on this budget to planned expenditure an institution will be aware of what staffing plans are affordable within their Chest allocation. If the account is in deficit an institution will need to identify an alternative source of funds to support planned expenditure. This process of monitoring expenditure and taking appropriate action is known as budgetary control.