Construction Accounting: Job Costing, Retainage & WIP Explained Guide

13 June 2025•10 min read•Viacheslav Muliukin

Construction accounting covers job costing, retainage, and WIP. KPMG found fewer than 30% of contractors produce accurate job cost forecasts on time. Here's how it works.

Construction accounting has a reputation for complexity that is partly earned and partly exaggerated. The earned part: construction involves long-term contracts, progress billing, retainage, joint ventures, and revenue recognition rules that do not apply to most other industries. The exaggerated part: once the core concepts are understood, the principles are consistent and learnable.

This guide covers the foundational concepts that every contractor, project manager, and construction finance professional needs to understand — cash vs accrual accounting, retainage, job costing, and work in progress — with enough specificity to be immediately useful.

⚡ TL;DRConstruction accounting differs from standard accounting in four key ways: percentage-of-completion revenue recognition, project-level job costing, retainage tracking, and WIP reporting. This guide explains each concept clearly, with practical examples relevant to UAE and international contractors.

⚡ TL;DR

KPMG found fewer than 30% of contractors produce an accurate job cost forecast within two weeks of a project milestone, with delayed field data as the primary bottleneck (KPMG Global Construction Survey, 2019)
Construction accounting requires percentage-of-completion revenue recognition under IFRS 15 and ASC 606 — not point-of-sale recognition
Retainage (typically 5%) is real money earned but not yet receivable: ignoring it in cash flow forecasts consistently overstates available cash
A WIP schedule is the most important financial document in a construction business and the one most commonly unavailable

Cash vs Accrual Accounting in Construction

Cash accounting records revenue when cash is received and expenses when cash is paid. Simple to maintain; gives a clear picture of actual cash position; does not match revenue and costs to the period when they were actually earned and incurred.

Accrual accounting records revenue when it is earned and expenses when they are incurred, regardless of when cash changes hands. More complex; gives a more accurate picture of financial performance; required for financial statements used by lenders and investors.

A contractor who completes 60% of a project in Month 3 but receives no payment until Month 4 (because the client has a monthly payment cycle with a 45-day processing lag) has earned significant revenue in Month 3 under accrual accounting — but received no cash. Under cash accounting, Month 3 looks like a loss-making period and Month 4 looks profitable, which is misleading.

For management decision-making — particularly cash flow forecasting — contractors need to track both the accrual position (what has been earned and owed) and the cash position (what has actually been received). These diverge on all but the simplest projects.

Percentage of completion method

Under IFRS 15 (international) and ASC 606 (US), revenue on long-term construction contracts is recognised based on the percentage of completion — typically measured as costs incurred to date as a percentage of total estimated costs. This means revenue recognition follows actual project progress, not billing milestones.

Job Costing: The Core of Construction Financial Management

Job costing is the process of tracking all costs associated with a specific project (job) separately from other projects and from general business overhead. It is the mechanism that answers the most important financial question in construction: did this project make money?

A job cost report shows

Contract value (original + approved variations)
Costs to date by category (labour, materials, plant, subcontractors, preliminaries)
Costs to complete (forecast — what will it cost to finish?)
Forecast final cost (costs to date + costs to complete)
Forecast margin (contract value minus forecast final cost)

The critical column is forecast final cost — not what has been spent, but what the project will cost when complete. A project that has spent AED 4M against a budget of AED 5M and has only 50% complete is not at 80% of budget — it is forecast to cost AED 8M against a AED 5M budget.

Cost codes and cost allocation

Every transaction — supplier invoice, labour timesheet, plant hire invoice, subcontractor payment application — must be allocated to the correct job and the correct cost code within that job. Poor cost code discipline produces job cost reports that are accurate in total but wrong in detail — the total project cost is right but the breakdown by trade or activity is unreliable.

The connection between field operations and job costing is often where contractors lose accuracy. Daily site records — workforce attendance, material deliveries, equipment utilisation — are the source data for cost allocation. When those records are incomplete or delayed, the job cost report lags behind reality. For more on structuring this process, see the guide to construction accounting software selection, which covers how field data integrates with financial systems.

A KPMG survey of global construction firms found that fewer than 30% of contractors could produce an accurate job cost forecast within two weeks of a project milestone, with most citing delayed field data as the primary bottleneck.

Source: KPMG — Global Construction Survey

Retainage (Retention): How It Works and Why It Matters

Retainage (also called retention) is a percentage of each progress payment withheld by the client until specific contractual milestones are reached — typically practical completion and the end of the defects liability period.

Standard retainage rates

5% of each progress payment, typically with a limit of 5% of the total contract value
Released in two tranches: 50% at practical completion, 50% at the end of the defects liability period (typically 12 months)

Contract value: AED 10,000,000 Retainage rate: 5%, capped at 5% of contract value = AED 500,000

Each payment application is reduced by 5% until AED 500,000 has been withheld. At practical completion, AED 250,000 is released. At the end of the 12-month defects period, the remaining AED 250,000 is released.

In the UAE, the Federal Law No. 6 of 2018 on Arbitration and construction-related contract frameworks under FIDIC both recognise retainage as a standard mechanism, though specific rates and release conditions vary by contract and emirate.

Source: UAE Ministry of Justice — Federal Legislation

Retainage receivable vs payable

Main contractors face retainage from both sides:

Retainage receivable: client withholds from the main contractor
Retainage payable: main contractor withholds from subcontractors

These two figures are not always equal — a main contractor who has a 5% retainage arrangement with the client but withholds 10% from subcontractors has a retainage payable float. This is a cash management position, not an unusual one.

The contractual terms governing retainage release are defined in the payment terms and defects liability clauses of each contract. Understanding those clauses in detail is covered in the guide to construction contract management and key clauses.

Work in Progress (WIP): The Financial Heartbeat of a Construction Business

The WIP schedule is a financial report that shows the status of every active construction contract at a specific date. It is the most important financial document in a construction business and the one most commonly misunderstood or unavailable.

The WIP schedule shows, for each contract

Column	Explanation
Contract value	Total value including approved variations
Estimated cost at completion	Current forecast of total project cost
Estimated gross margin	Contract value minus estimated cost at completion
% complete	Typically: costs to date divided by estimated cost at completion
Revenue earned to date	Contract value x % complete
Revenue billed to date	Actual invoices issued
Over/under billing	Revenue billed minus revenue earned (positive = over-billed; negative = under-billed)

Over-billing and under-billing

Over-billing: The contractor has billed more than they have earned. This creates a liability — the contractor owes the client work to earn the excess billing. From the client's perspective, this is an advance payment.
Under-billing: The contractor has earned more than they have billed. This creates an asset — the contractor is owed money for completed work. Under-billing is common in construction, particularly when billing cycles lag behind construction progress.

Why the WIP matters for external reporting

Lenders and bonding companies use the WIP schedule to assess a contractor's financial health — not just whether the business is profitable, but whether it is consistently earning its billings or accumulating underbillings that could become losses. A WIP schedule with consistently large underbillings on multiple projects is a warning sign that the contractor is under-billing to avoid difficult conversations, and that the apparent profit may be overstated.

Common Construction Accounting Mistakes

Not updating cost-to-complete estimates: The forecast final cost is only as good as the cost-to-complete estimate. If cost-to-complete estimates are not updated as the project progresses — or if site managers are optimistic about how much work remains — the WIP schedule will overstate the expected margin until the final account makes the problem visible.

— "When we worked with a UAE general contractor managing 12 concurrent projects worth AED 380M in total, their retainage receivable balance had not been properly tracked for 18 months. Reconciling it took three weeks. Building a simple retainage ledger in their accounting system prevented the same problem recurring — and freed up AED 8M they didn't know they were owed." — Viacheslav Muliukin, Founder & CEO, Banamind

Frequently Asked Questions

What is the difference between cash and accrual accounting in construction?

Cash accounting records income when cash is received and expenses when cash is paid. Accrual accounting records revenue when it is earned and costs when they are incurred, regardless of payment timing. For construction — where projects run for months and billing lags behind work — accrual accounting gives a far more accurate picture of financial performance, which is why it is required for financial statements used by lenders and bonding companies.

What is job costing in construction?

Job costing is the process of tracking all costs — labour, materials, plant, subcontractors — to a specific project, separately from other projects and general overhead. It answers whether each individual project made or lost money, and at what margin. Without job costing, a contractor can be profitable overall while losing money on specific projects without realising it.

How does retainage work in construction contracts?

Retainage is a percentage (typically 5%) withheld from each progress payment until practical completion and the end of the defects liability period. It protects the client against incomplete work. For the contractor, it represents real money earned but not yet receivable — and must be tracked carefully in cash flow forecasts to avoid overestimating available cash.

What is a WIP schedule and why do lenders require it?

A Work in Progress (WIP) schedule shows the status of every active construction contract at a specific date — what has been earned, what has been billed, and whether the contractor is over- or under-billed. Lenders require it because it reveals whether reported profits are backed by real project performance, or whether large underbillings are masking potential losses.

What is the percentage of completion method?

Under IFRS 15 and ASC 606, revenue on long-term construction contracts is recognised proportionally as the project progresses — typically measured as costs incurred to date divided by total estimated costs. This aligns recognised revenue with actual project completion rather than billing dates, giving a more accurate picture of financial performance across reporting periods.

How Banamind Supports Construction Financial Records

Banamind captures daily site activity — workforce, deliveries, progress, issues — which forms the documentation layer supporting accurate cost allocation and progress billing. Field data from Banamind reduces the reconciliation effort between site activity and financial records.

Banamind is not accounting software and does not replace your accounting system. It handles the field capture layer: structured daily records, photo evidence, and delivery logs that feed into your accounting software with less manual re-entry. For invoicing with attached progress proof, see the Invoicing with Proof of Work feature.

Last updated: May 2026