Top 6 Types of Construction Billing Methods and Uses

Construction billing determines how a contractor calculates what a customer owes, when invoices are issued, and what evidence supports each payment claim.

The right structure depends on the contract. A fixed-price project may use progress invoices, while another project may bill actual labour and materials. Retention, advance payments, change orders, and VAT can then affect the amount billed or collected at each stage.

For Saudi contractors, the billing process must also account for the Kingdom’s 15% VAT rules for construction and contracting services, including specific treatment for progress claims, advance payments, retention, and certain government contracts.

This guide explains six common construction billing methods, when each works best, their advantages and risks, and the Saudi billing and VAT rules contractors should consider before issuing an invoice.

For related project-cost controls, see HAL’s Construction Cost Management guide.

Key Takeaways

• Lump sum, time and materials, cost-plus, and unit price determine how project charges are calculated, while progress and advance billing determine when amounts are invoiced.
• The right method depends on scope certainty, measurement requirements, cost risk, contract terms, and how work will be certified.
• Retention and penalties affect project payments but are contract mechanisms, not separate billing methods.
• Saudi construction services are generally subject to 15% VAT, with specific rules for progress claims, advance payments, retention, and qualifying government contracts.
• HAL can support progressive invoicing, project costs, retention tracking, expenses, receivables, and VAT/e-invoicing workflows when configured around the contract.

What Is Construction Billing?

Construction billing is the process of calculating, documenting, invoicing, and collecting amounts due under a construction contract.

Unlike simple product invoicing, a construction invoice may depend on:

• Work completed
• Measured quantities
• Labour and material costs
• Contract milestones
• Approved variations
• Previous payments
• Advance payments
• Retention
• VAT
• Completion or progress certificates

In Saudi commercial practice, a construction completion or progress report may also be referred to as a Mustakhlas. ZATCA describes this as a document used to determine the amount payable for part of a construction project and obtain the customer’s approval. It is not automatically the same thing as the formal tax invoice.

Construction Pricing Method vs Billing Method

These terms are often mixed together, but they answer different questions.

A project can therefore use more than one approach at the same time.

For example, a contractor may have a lump-sum contract but issue monthly progress invoices and have 5% retention withheld from each certified payment.

Why Construction Billing Matters

A structured billing process helps contractors:

• Link payment claims to completed or certified work.
• Reconcile billed amounts against budgets and project costs.
• Track outstanding receivables and retained balances.
• Document approved changes and variations.
• Apply VAT consistently.
• Give customers a clearer basis for reviewing and approving payment claims.

The billing method should therefore follow the contract rather than being selected independently after work begins.

Top 6 Construction Billing Methods

Construction projects often combine a pricing basis with a billing schedule. The six approaches below cover the most common ways project charges are calculated or invoiced.

1. Lump-Sum or Fixed-Price Billing

Under a lump-sum contract, the contractor agrees to deliver the defined scope for an agreed total price.

The customer may still pay that price through several progress invoices rather than one invoice at completion.

Best suited for:

• Clearly defined scopes
• Complete drawings and specifications
• Projects where quantities and deliverables are reasonably predictable

Advantages:

• Gives the customer greater price certainty for the agreed scope.
• Makes contract-value tracking straightforward.
• Rewards efficient cost and resource management by the contractor.

Risks:

• Contractors carry more cost risk when actual costs exceed estimates.
• Changes outside the agreed scope require proper variation or change-order control.
• Poorly defined scope can create disputes over what the fixed price includes.

2. Time and Materials (T&M) Billing

Under time and materials billing, the customer is charged based on actual labour time and materials used, according to rates defined in the contract.

Best suited for:

• Maintenance and repair work
• Emergency work
• Projects where the final scope cannot be defined reliably in advance

Advantages:

• Accommodates changing requirements.
• Connects billing to actual resources consumed.
• Makes additional work easier to account for when properly documented.

Risks:

• Final cost is less predictable.
• Accurate timesheets, material records, and approvals are essential.
• Customers may require spending caps or pre-approval for additional work.

3. Cost-Plus Billing

Under a cost-plus arrangement, the customer reimburses allowable project costs and pays the contractor an additional agreed fee.

That fee may be structured as a fixed amount, percentage, or another contractually defined basis.

Best suited for:

• Complex projects with uncertain scope
• Projects started before the full design is finalized
• Work where actual costs need to remain transparent

Advantages:

• Accommodates uncertain project costs.
• Gives the customer visibility into qualifying expenditures.
• Reduces some pricing risk for the contractor.

Risks:

• Requires clear definitions of allowable and non-allowable costs.
• Documentation and audit requirements can be substantial.
• Weak cost controls can cause the total project cost to rise.

4. Unit-Price Billing

Under unit-price billing, the parties agree a price for each measurable unit of work.

The amount billed is then based on:

Agreed unit price × verified quantity completed

Examples may include:

• Cubic metres of excavation
• Metres of pipe
• Square metres of flooring
• Number of installed fixtures

Best suited for:

• Civil works
• Roads and utilities
• Projects where quantities may vary but work units can be measured reliably

Advantages:

• Billing reflects measured quantities actually completed.
• Works well when final quantities are uncertain at contract award.
• Progress can be linked directly to measurable units.

Risks:

• Quantity measurement and certification must be accurate.
• Final contract value can change significantly if quantities differ from estimates.
• Measurement disputes can delay payment.

5. Progress or Milestone Billing

Progress billing allows the contractor to invoice portions of the contract value as work progresses.

Invoices may be based on:

• Percentage completion
• Defined milestones
• Measured work
• Certified monthly progress
• A schedule of contract activities

ZATCA’s current contracting guidance recognizes that construction services are generally continuous supplies and that multiple invoices or interim payments can create separate VAT due dates during the project. (ZATCA Contracting Sector VAT Guideline)

Best suited for:

• Long-duration projects
• Large construction contracts
• Projects with measurable stages or monthly certification

Advantages:

• Provides contractors with cash inflows during project execution.
• Links customer payments to documented progress.
• Reduces the need to wait until project completion for the entire contract value.

Risks:

• Completion percentages or quantities must be supported.
• Delayed certification can delay invoicing and collection.
• Previous billings, retention, variations, and VAT must be reconciled carefully.

HAL itself supports progressive invoicing, allowing a percentage of a sales-order amount to be invoiced progressively. (HAL Progressive Invoice documentation)

6. Advance or Prepayment Billing

Advance billing occurs when the customer pays part of the contract amount before the related work is completed.

Construction contracts may use advances to support:

• Mobilization
• Initial material procurement
• Site setup
• Other agreed startup costs

The advance is normally deducted from later progress claims according to the contract.

Advantages:

• Gives contractors working capital before major project costs are incurred.
• Can reduce early-stage cash-flow pressure.
• Provides funding for mobilization and procurement where the contract allows it.

Risks:

• The contract must clearly explain how the advance will be recovered.
• Customers may require an advance-payment guarantee.
• Finance teams must avoid double-counting the advance when later invoices are raised.

Saudi VAT Note on Advance Payments

Advance payments can create a VAT obligation before the related construction work is completed.

ZATCA’s current contracting guideline gives an example where a contractor receives a down payment for future construction work and must calculate VAT and issue a tax invoice for the amount received. (ZATCA Contracting Sector VAT Guideline)

The advance must then be accounted for correctly when subsequent progress invoices are prepared.

Construction and contracting services relating to real estate in Saudi Arabia are generally subject to VAT at the standard 15% rate. (ZATCA Contracting Sector VAT Guideline)

The billing method can affect when VAT becomes due, so finance teams should not treat invoicing and VAT as separate processes.

Progress and Continuous Billing

Construction services are generally treated as continuous supplies.

Depending on the contract, VAT can become due based on events such as:

• The contractual payment due date
• Issuance of the tax invoice
• Receipt of payment

ZATCA’s current guideline explains that individual interim payments or invoices can create separate VAT due dates during a construction project.

Retention

Retention does not automatically reduce VAT on an amount that has already been fully invoiced.

If the contractor issues a tax invoice for the full amount due, VAT is due on the full invoiced amount, even if the customer withholds part of the payment as retention.

When that retained balance is later released, ZATCA states that there is no separate obligation to issue another invoice or declare VAT again merely because the retained cash is paid. (ZATCA retention guidance)

For a worked example and invoice format, see HAL’s Retention Invoice Template for Saudi Arabia article.

Advance Payments

Where an advance payment represents consideration for future taxable construction services, receipt of that payment can trigger VAT and a related tax-invoice requirement.

Contracts With Government Entities

Certain supplies made directly to Saudi government entities under contracts governed by the Government Tenders and Procurement Law have special VAT timing rules.

For qualifying claims, VAT generally becomes due on the payment-order date or the date payment is received, whichever occurs earlier. The special treatment applies to the main contractor contracting directly with the government entity, not automatically to its subcontractors. (ZATCA guidance for government contractors)

Because billing structures can differ significantly between private, subcontract, and government projects, tax treatment should be reviewed against the actual contract.

Common Challenges in Construction Billing & How to Overcome Them

Construction billing can often create delays, cash flow issues, and confusion if not handled carefully. Here is a detailed look at common challenges you may face and how to tackle them effectively:

1. Incomplete or Incorrect Records

Missing or inaccurate details in invoices, like wrong quantities or dates, can cause payment disputes and slow down cash flow.

How to Overcome It:

• Keep complete records of all work, materials, and labor.
• Use digital tools or billing software, like HAL, to automatically track transactions and prevent errors.

2. Unapproved Change Orders

Projects often evolve, and work outside the original scope can cause billing errors if not formally approved.

How to Overcome It:

• Always get written approval for any changes before invoicing.
• Maintain a change order log to track adjustments and communicate clearly with clients.

3. Holdbacks and Retainage

Clients may withhold a portion of payment until project milestones or final approvals are met, impacting cash flow.

How to Overcome It:

• Understand retainage terms in your contracts.
• Plan your cash flow around holdbacks to avoid shortages in materials or wages.
• Consider using HAL to monitor holdbacks and manage retainage efficiently.

4. Fluctuating Material Costs

Material prices can change during a project and reduce contractor margins, particularly under fixed-price arrangements.

However, a higher material cost does not automatically mean the contractor can increase the customer’s invoice.

How to Overcome It:

• Review escalation, variation, and change-order provisions before signing the contract.
• Track estimated, committed, and actual material costs throughout the project.
• Obtain written approval before billing changes that fall outside the original scope or price.
• Use procurement planning and approved alternative suppliers where contract specifications allow substitutions.
• Reflect approved variations in both the project budget and subsequent billing records.

HAL’s newer Construction Cost Management guide specifically documents project budgets versus actual costs, committed spending, subcontractor billing, retention, and change-order tracking.

5. Outdated Billing Systems

Manual invoicing or old software increases errors, slows approval, and makes tracking payments difficult.

How to Overcome It:

• Move to modern digital billing solutions that automate tracking and approvals.
• Ensure your system allows for real-time updates and reporting for faster decisions.

6. Payment Delays

Late payments are common in construction and can disrupt your project cash flow, delaying work or procurement.

How to Overcome It:

• Clearly define payment terms in contracts.
• Use automated reminders and maintain proactive communication with clients to follow up on payments.

7. Complex Payment Terms

Milestone payments, retainage, and layered contracts can be confusing and lead to miscalculations.

How to Overcome It:

• Use billing software that aligns with your contract terms.
• Break down complex payments into simple schedules for easy tracking.

8. Poor Communication and Collaboration

Misunderstandings between contractors, subcontractors, and clients often lead to billing mistakes and disputes.

How to Overcome It:

• Keep all communication centralized in one platform or software.
• Hold regular project meetings and ensure everyone has access to the latest billing information.

If these challenges sound familiar, it’s time to upgrade how your construction billing works. HAL helps you manage everything, from project expenses and intercompany billing to VAT compliance and financial reporting, under a single, easy-to-use system.

These common issues can slow down any project, but real-world examples reveal practical ways to overcome them effectively.

Case Study: Jash Holding - Making Billing Clear, Fast, and Reliable

Jash Holding, through its subsidiary Jash Technical Services (JTS), operates in facilities management, contracting, logistics, and manufacturing with over 4,000 employees across five companies. They needed a modern solution to unify operations and simplify financial management.

The Challenge

• With multiple companies and legacy systems, Jash faced fragmented data, slow workflows, and little visibility into intercompany transactions.
• Managing payroll, project costs, subcontracting, and inventory across divisions became time-consuming and error-prone, causing payment delays.

The Solution

By implementing HAL ERP, Jash streamlined its operations with modules for:

• HR & Payroll: Automated contracts, leave, and end-of-service benefits.
• Project Costing & Mobilisation: Clear staff allocation and profitability tracking.
• Procurement & Subcontracting: Smooth vendor management and integrated billing.
• Intercompany Transactions: Automated internal billing with VAT support.
• Consolidated Reporting & Inventory: Real-time P&L, dashboards, and accurate site-level stock tracking.

The Result

According to HAL’s published Jash Holding case material, the implementation delivered:

• More than 60% improvement in operational efficiency
• Better visibility into project costs and profitability
• Reduced manual data entry and reconciliation work
• Faster reporting and decision-making
• Improved coordination across multiple subsidiaries

HAL’s Jash Holding case study describes how the group replaced fragmented legacy workflows with connected finance, project, payroll, procurement, inventory, and intercompany processes.

These results relate to the broader ERP implementation rather than one billing feature alone, so the case is best used as evidence of integrated project and financial management.

How HAL Supports Construction Billing and Project Finance

Construction billing works best when invoices are connected to the underlying project costs, contracts, receivables, approvals, and tax records.

HAL Contracting brings project and financial workflows into the same ERP environment. HAL’s current construction content documents support for project costing, subcontractors, procurement, retention tracking, project expenses, and multi-company operations.

Relevant capabilities include:

• Progressive invoicing: HAL supports percentage-based progressive invoices against sales orders. (HAL invoice types)
• Project cost tracking: Compare project labour, procurement, subcontractor, equipment, and operating costs against budgets through HAL Contracting.
• Expense management: Capture and approve project and employee expenses through HAL Expenses.
• Accounting and receivables: Connect invoices and financial entries through HAL Accounting.
• VAT and e-invoicing: Support Saudi ZATCA e-invoicing workflows through HAL VAT Care.
• Multi-company reporting: Manage separate entities and consolidated reporting through HAL Group Company Central.

HAL can support the operational workflow, but the correct billing basis, variation entitlement, retention terms, and VAT treatment still depend on the underlying contract and applicable rules.

Conclusion

Construction billing starts with the contract.

A contractor first needs to determine how the contract price is calculated—for example, lump sum, time and materials, cost-plus, or unit price—and then determine when amounts will be invoiced, such as through progress claims or advance billing.

Retention, approved variations, previous payments, and VAT must then be reflected correctly in each payment claim.

For Saudi projects, contractors should pay particular attention to the ZATCA VAT rules for construction and contracting, especially where the project involves progress invoices, advance payments, retention, or government contracts.

HAL Contracting can connect project costing, subcontractors, procurement, invoicing, expenses, accounting, and multi-company financial workflows in one system.

Businesses evaluating how HAL would fit their construction billing process can request a HAL ERP demo.

Frequently Asked Questions

1. What is the best construction billing method?

There is no single method that is best for every project.

Lump sum is often suitable when the scope is clearly defined, while time and materials or cost-plus arrangements can work better when scope or costs remain uncertain. Unit-price billing is useful when completed quantities can be measured, and progress billing is commonly used on longer projects.

2. Can a project use more than one billing method?

Yes.

For example, a project can have a lump-sum contract price, use monthly progress invoices, receive an advance payment, and have retention withheld from certified payments.

These mechanisms perform different functions and can operate together.

3. Is retention a construction billing method?

Not really.

Retention is a contractual payment mechanism where part of an amount due is withheld until specified completion or performance conditions are satisfied.

It can apply alongside lump-sum, unit-price, cost-plus, or progress billing.

4. How does VAT apply to construction progress invoices in Saudi Arabia?

Saudi construction services are generally subject to 15% VAT.

Because construction is typically treated as a continuous supply, interim invoices, contractual due dates, or payments can create VAT due dates during the project. Certain government contracts have separate timing rules.

5. Can contractors increase invoices when material prices rise?

Not automatically.

Whether additional costs can be passed to the customer depends on the contract, including any escalation, variation, or change-order provisions. Contractors should document cost changes and obtain the required approval before billing amounts outside the agreed scope or price.

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