Imagine you budgeted ₹10,00,000 for a month when you planned to produce 10,000 units — but you actually produced only 7,000 units. If you compare actual costs against that original ₹10,00,000 budget, the comparison is unfair and misleading. That's the exact problem a Flexible Budget solves.
A Flexible Budget (also called a Dynamic Budget) is a budget that automatically adjusts to the actual level of activity. Instead of locking in one output level, it prepares a series of budgets — or a formula — that tells you what costs should have been at whatever level you actually achieved. The core insight is simple: Fixed Costs don't change with output, but Variable Costs do. A flexible budget honours this reality; a Fixed (Static) Budget ignores it. Semi-variable costs are split into their fixed and variable components using methods like the High-Low method before plugging them in.
The real power of a flexible budget shows up in performance evaluation. At month-end, Rajesh & Co. Pvt. Ltd. produced 7,000 units instead of the budgeted 10,000. You flex the budget down to 7,000 units — recalculate what variable costs should be at that level, keep fixed costs the same — and then compare against actuals. The gap you get now is a genuine spending variance, not a fake volume-driven difference. This is asked frequently as a 4-mark or 8-mark question in Paper 4, either as a standalone flexible budget preparation or as the first step before computing variances.
The preparation steps are: (1) Classify all costs as Fixed, Variable, or Semi-variable. (2) Express variable costs as a cost per unit (or per machine hour / labour hour — whichever activity base is used). (3) For any given activity level, Budget Cost = Fixed Cost + (Variable Cost per unit × Actual Units). (4) Present budgets at multiple levels (say 70%, 100%, 120% of capacity) in a columnar format. The ICAI Study Material typically presents this as a table with activity levels across the top and cost heads down the side — practise that layout until it's second nature.