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GST Correction Factor for DSR & Bill Deductions

Where CPWD's 0.973 factor comes from — the two rate build-ups set side by side, worked live on your own figures — and how GST, labour welfare cess and TDS are worked back out of a gross bill amount.

What changed. CPWD revised how GST enters the analysis of rates (order dated 08 August 2024, File No. 158/SE(TAS)/GST/2024/02-E). Under the earlier method GST was added inside the build-up — before contractor's profit & overheads and before labour cess — so those two were charged on a GST-inclusive figure. Under the revised method GST is applied last, on the completed rate. Nothing about the work changes; only the order of the steps does, and that alone makes the finished rate slightly lower. Rather than re-derive every item, the order fixes a single modification factor of 0.973 to apply to the existing DSR 2023 rates.
× 0.973
Modified rate = DSR 2023 rate × 0.973  ·  derived below, and reproducible on any base figure

A · Where 0.973 comes from

Both build-ups start from the same base rate and end with a gross figure. The factor is simply one gross divided by the other. Change the base below and watch it hold — the factor is a ratio, so it is the same whatever you start from.

Work it out on your own base rate

Reading the two columns. The only difference is where GST enters. Existing: base → water charges → GST → CP&OH → labour cess. Modified: base → water charges → CP&OH → labour cess → GST. Because CP&OH (15%) and labour cess (1%) no longer sit on top of a GST-inclusive figure, the finished rate falls by 2.7%.

B · Working GST, cess and TDS back out of a bill

The tendered value an agency quotes already contains GST on the works contract and labour welfare cess. To deduct each correctly you first have to strip them back out of the gross, in the right order — each divisor applies to what is left after the previous one (procedure per OM 158/SE(TAS)/GST/2024/314-H dated 03.10.2024).

Deductions on gross work done

Amount for GST deduction (G) = U ÷ 1.18 Amount for LWC deduction (L) = U ÷ (1.18 × 1.01) Amount for TDS deduction (T) = U ÷ (1.18 × 1.01 × 1.02)

Each line strips one more component: 1.18 removes the 18% GST, the further 1.01 removes the 1% labour welfare cess, and the further 1.02 removes the 2% element carried in the tendered value before income-tax TDS is worked out. Deduct each at its own rate on the corresponding amount above — not on the gross.

These figures are an educational aid for quick checks. The governing text is CPWD's own order (08.08.2024, File No. 158/SE(TAS)/GST/2024/02-E, and OM 158/SE(TAS)/GST/2024/314-H dated 03.10.2024) read with your schedule of rates and the contract — always verify against those before applying a factor to a sanctioned estimate or a deduction to a bill. Rates of GST, cess and CP&OH are those current when the order issued; check for later revisions.
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