What actually happens between the day work is measured at site and the day the contractor's cheque is prepared — cumulative quantities, part rates, recoveries, secured advance and the final bill, explained the way a works office runs them.
A works contract of any size runs for months, sometimes years. No contractor can finance the entire job out of pocket and wait for a single settlement at the end, so departments pay in instalments as the work progresses. Each instalment is a running-account (RA) bill — an on-account payment against work actually measured, never a final settlement of any item. Understanding that one phrase, "on account", explains almost everything about how RA bills are structured, why they are cumulative, and why the final bill behaves so differently from the ones before it.
Every rupee paid on a works bill must trace back to a recorded measurement. The measurement book (MB) is the original — and legally the only — record of work done. The junior engineer records measurements at site, in ink, giving the date, the location of the work, the item particulars and the dimensions from which each quantity is computed. The contractor or his authorised agent signs the measurements in token of acceptance, and a senior officer test-checks a prescribed percentage of them before payment. An abstract at the end of each set of measurements carries the item-wise quantities forward to the bill.
Because the MB is a payment document, the discipline around it is strict: no pencil entries, no overwriting (corrections are scored through and initialled), no leaving pages blank, and no recording measurements from memory days after the event. Where the department permits computerised measurement sheets, they are certified and bound back to the MB reference. A tidy measurement sheet that shows number × length × breadth × depth for every entry saves hours at checking time.
An RA bill does not record only the work done since the last bill. Against every item it records the full up-to-date quantity executed from commencement of the work. The amount payable now is then derived by subtraction:
Suppose an agreement provides 100 m³ of M15 (1:2:4) foundation concrete. The first bill measures 40 m³ and pays for 40. By the second bill the cumulative quantity is 90 m³ — so the bill shows 90 m³ up to date, and the payment works out on the 50 m³ executed since the previous bill. Now suppose a checking officer finds the first bill had over-recorded 2 m³. Nothing special needs to be done: the correct up-to-date figure of 88 m³ goes into the next bill, and the subtraction automatically recovers the excess. This self-correcting property is the whole point of cumulative billing — every bill re-states the complete account, so an error never survives beyond the bill in which it is noticed. It also means the account can always be read against the agreement quantities at a glance, which matters for deviation control.
Work rarely completes in the neat slices an item schedule imagines. Plaster may be done but the final coat of paint pending; a roof slab cast but its finishing incomplete; doors fixed but hardware awaited. Withholding all payment would starve the contractor of legitimate working capital; paying the full agreement rate would leave the department unsecured for the balance work. The answer is a part rate: a stated fraction of the agreement rate, applied to the measured quantity — or to a specified portion of it — until the item is completed.
Two rules keep part rates safe. First, the rate allowed must be justified in writing and must leave enough margin that the remaining operations can, if necessary, be completed at the contractor's risk and cost from the withheld amount. Second, the part rate is provisional: when the item is finished, a later bill simply pays the same quantity at the full rate and the cumulative arithmetic releases the balance. Restoring the full rate before completion is one of the quickest ways to attract an audit paragraph.
Before any bill is passed, each item's up-to-date quantity is compared with the quantity provided in the agreement. Small variations are normal — estimates derive from drawings, and sites have their own opinions — but once an item exceeds its agreement quantity beyond the permissible deviation limit, payment for the excess needs a sanctioned deviation statement, and the rate for quantities beyond the threshold may fall to be re-determined rather than paid at the agreement rate. The mechanics of deviation limits, and how a deviation statement is drawn up, are covered in a separate article on deviations and extra items. Remember also that where the contract was tendered at a premium or rebate on scheduled rates, that percentage is already built into the agreement rates in the bill — it is never applied a second time.
The gross value of work is only the top line. Between it and the cheque sits a column of recoveries, each with its own logic:
| Deduction | How it works |
|---|---|
| Security deposit (SD) | A percentage of the gross value of work is withheld from every bill until the full deposit prescribed by the contract has accumulated. Some contracts permit part or all of it to be replaced by a bank guarantee. |
| Advances recovery | Mobilisation or plant advances, where granted, are recovered in instalments on the schedule fixed in the contract, generally with interest. |
| Departmental materials | Where the department issues cement, steel or other stipulated materials, their cost at the agreed issue rates is recovered through the bills. Recovery in running bills is normally regulated by the theoretical consumption for the work actually done, so the account stays in step with progress. |
| Secured-advance recovery | Any secured advance outstanding on materials is written back as those materials are consumed into measured work (see below). |
| Statutory deductions | Deductions required by the law in force — tax deducted at source, labour-welfare cess and the like — are made at the rates applicable on the date of payment. |
| Other recoveries | Hire of departmental machinery, water and power supplied to the contractor, and any compensation for delay levied under the contract. |
Each of these is itself cumulative: the bill shows the total recoverable up to date and the amount already recovered, and deducts the difference. The same subtraction discipline that protects quantities protects recoveries.
Work sometimes demands an item the agreement never priced — an extra item — or requires an agreement item to be executed in a materially different way — a substitute item. Neither can simply appear in a bill. The rate is first derived: from analogous agreement rates where a fair derivation exists, otherwise from the schedule of rates adjusted by the tender percentage, and failing both, by a market-rate analysis of rates supported by quotations. The derived rate is sanctioned by the authority competent under the delegation of financial powers, and only then does the item join the bill — listed in its own section so that the original agreement work and the sanctioned additions remain distinguishable to the last bill.
A contractor who has brought a large lot of steel or aggregate to site has locked up money in work not yet measurable. Most works contracts therefore allow a secured advance: an on-account payment against non-perishable materials brought to site for incorporation in the work, usually limited to a contract-specified fraction — commonly about three-quarters — of their assessed value, and never for quantities beyond the reasonable requirement of the balance work. The materials stand hypothecated to the department under an indemnity bond, must be stored and watched properly, and the advance is recovered bill by bill as the materials are consumed into measured work. Perishable materials, and materials whose value cannot be verified, are outside its scope. Like everything else in an RA bill, the secured advance is cast cumulatively: each bill states the advance admissible on materials now at site, and the difference from the previous bill is what is actually paid or recovered.
The final bill is where "on account" ends and settlement happens. Everything provisional must resolve to zero or to its true value:
None of these objections requires brilliance to avoid — only a bill that carries its own history correctly. That is precisely what cumulative billing was designed for, and precisely what breaks when carry-forwards are done by hand at month-end pressure. A structured billing tool that locks the previous bill, derives the since-previous quantities automatically and forces the final-bill recoveries to resolve — as the eTAB Works-Estimator™ billing module does — turns the audit checklist from a worry into a by-product. Before you sign the next bill, run it against our printable bill-checking checklist.