Planning and controlling are two complementary functions of management. Planning is a function of setting standards which serve as the basis of controlling. Once a plan becomes operational, controlling is necessary to monitor the progress, measure it, discover deviations and initiate corrective measures to ensure that events conform to plans. Thus, planning without controlling is meaningless.
In the same way controlling is blind without planning. If the standards are not set in advance, managers have nothing to control. When there is no plan, there is no basis of controlling. Thus planning and controlling are closely related.

Planning and controlling also have some reciprocal relationship. And they are:
1) Planning is prescriptive whereas, controlling is evaluative: Planning is basically an intellectual process involving thinking and analysis to discover and prescribe an appropriate course of action for achieving objectives. Controlling, on the other hand, checks whether decisions have been translated into desired action.

2) Planning is looking ahead while controlling is looking back: Plans are prepared for future and are based on forecasts about future conditions. Therefore, planning involves looking ahead and is called a forward-looking function. On the contrary, controlling is like a postmortem of past activities to find out deviations from the standards. In that sense, controlling is a backward-looking function.