Mixed Invoice Template
Most project engagements are not purely one billing type. A marketing campaign might involve an hourly strategy phase followed by fixed-fee production milestones. A software project might include a time-and-materials development phase and a fixed-fee deployment phase. When your billing spans multiple methodologies, sending separate invoices for each is administratively cumbersome and creates a fragmented financial record. A mixed invoice consolidates all billing types into a single, professionally organized document. Eonebill's mixed invoice template gives you the structure to present time-based and fixed-fee charges in a single invoice that clients can review and approve quickly.
What Is a Mixed Invoice?
A mixed invoice is a billing document that combines two or more billing methodologies in a single invoice. The most common combination is time-based billing (hourly rates for logged hours) with fixed-fee billing (flat amounts for specific deliverables or milestones). The mixed invoice brings these different charge types together in a single, organized document.
The mixed invoice exists because project work rarely fits into a single billing box. Clients want a single invoice that covers all the work performed. Providers want to bill using the most appropriate method for each type of work without creating administrative complexity. The mixed invoice resolves this by presenting all charges in one place, organized by type.
Key Sections of a Mixed Invoice
Header with Invoice Identification
Standard invoice header: your business details, client details, invoice number, date, and due date. Add a billing period label to clarify which work is being billed.
Billing Type Labels
Distinguish between billing types using clearly labeled section headers: "HOURLY / TIME-BASED CHARGES" and "FIXED-FEE / DELIVERABLE CHARGES." This organization is the core structural feature of the mixed invoice and what makes it readable.
Time-Based Charges Section
For each hourly line item, include the date, task description, hours worked, hourly rate, and line total. Present these in a table format with columns for each data point. Summarize the total hours and total time-based charges at the bottom of this section.
Fixed-Fee Charges Section
For each fixed-fee charge, include the deliverable description and the flat amount. If the fixed fee is tied to a milestone, reference the milestone number or title. Summarize the total fixed-fee charges at the bottom of this section.
Expense or Disbursement Section (if applicable)
If there are reimbursable expenses or disbursements, include them in a separate section with the same level of detail as the other charge types.
Grand Total Summary
Combine all sections: total hourly charges, total fixed-fee charges, total expenses, applicable taxes, and grand total. This summary is what the client looks for when approving payment — make it prominent.
How to Create a Mixed Invoice
- Track all work by billing type throughout the project. Maintain separate records for time-based work and fixed-fee deliverables. When billing day arrives, you need these records readily available and clearly separated by type.
- Group line items by billing type in the template. Enter all time-based charges in the hourly section and all fixed-fee charges in the fixed-fee section. Do not intermingle them — the grouping is what makes the invoice readable.
- Label each section clearly. Use bold section headers so the client can immediately distinguish between billing types. This visual organization prevents confusion and reduces payment delays.
- Calculate section subtotals. Sum the hourly section separately from the fixed-fee section before combining them in the grand total. Showing these subtotals helps the client verify each billing type independently.
- Add a summary section. Build a clean summary table that shows the grand total broken down by billing type. This is the reference point the client's accounts payable team uses to code the invoice for approval.
- Review for completeness. Before sending, verify that all time entries and fixed-fee milestones are included. Missing a charge on a mixed invoice means reissuing a supplemental debit invoice — which creates extra work for you and frustration for the client.
Sample Mixed Invoice
> FROM: Helix Engineering Group
> 2200 Industrial Parkway
> Portland, OR 97201
> billing@helixeng.com
>
> BILL TO: Cascade Regional Hospital
> 800 Healthcare Boulevard
> Portland, OR 97202
> Attn: Materials Management
>
> Invoice #: MI-2024-0058
> Date: July 31, 2024
> Billing Period: July 1–31, 2024
> Due Date: August 15, 2024
>
> ---
>
> SECTION 1: TIME-BASED CHARGES (Hourly)
>
> | Date | Description | Hours | Rate | Amount |
> |---|---|---|---|---|
> | Jul 3 | Site assessment and feasibility review | 8.0 | $185 | $1,480.00 |
> | Jul 8 | Schematic design development | 12.5 | $185 | $2,312.50 |
> | Jul 15 | Client design review meeting | 4.0 | $185 | $740.00 |
> | Jul 22 | Permit application preparation | 9.0 | $185 | $1,665.00 |
> | Section 1 Subtotal | | 33.5 | | $6,197.50 |
>
> ---
>
> SECTION 2: FIXED-FEE DELIVERABLE CHARGES
>
> | Description | Amount |
> |---|---|
> | Milestone 2 — Schematic Design Package (flat fee per Contract Section 4.2) | $8,500.00 |
> | Milestone 2 Reimbursable Expenses — Printing, plotting, delivery | $340.00 |
> | Section 2 Subtotal | $8,840.00 |
>
> ---
>
> INVOICE SUMMARY
>
> | | |
> |---|---|
> | Total Time-Based Charges: | $6,197.50 |
> | Total Fixed-Fee Charges: | $8,840.00 |
> | Grand Total Due: | $15,037.50 |
>
> Remit to: Helix Engineering Group, U.S. Bank, Routing #122105278, Acct #887654312
> Questions? billing@helixeng.com | 503-555-0182
Related Templates
- Time and Materials Invoice Template — For time plus materials billing
- Hourly Invoice Template — For pure hourly billing
- Milestone Invoice Template — For fixed-fee milestone billing
- Professional Invoice Template — General professional billing
- Consulting Invoice Template — Consulting engagements