Invoice Flow app icon Invoice Flow management Get the app
EN

From One-Off HR Projects to Retained People Partner

By Michelle Park, HR Consultant — Seattle, WA

I spent twelve years in HR leadership — HR director at a mid-size tech company, then VP of People at a fintech startup through a Series B. In 2019, I left to consult independently. The demand for fractional HR leadership was real: small and mid-size companies that needed senior HR capability without a full-time senior HR hire.

What I didn’t anticipate was the billing model problem. Corporate HR doesn’t bill. I had no framework for what to charge, how to structure engagements, or what invoices should look like for the work I was doing.

My first year as an independent HR consultant was professionally successful and financially disorganized. I completed eight projects. I was paid for seven. The eighth — an 8-week handbook and policy development engagement for a 40-person technology company — ended with a dispute over scope. The client said the work delivered didn’t match what they’d expected. I had no written scope in the invoice to contradict them. We settled the dispute by cutting the invoice 40%. I absorbed a $4,200 loss on a $10,500 engagement.

The problem was not the client’s interpretation of the scope. The problem was that I had never documented the scope.

Building a Billing Structure for HR Consulting

After the dispute, I restructured the practice around three billing models:

Project Engagements (defined scope):

Fractional HR Retainer (ongoing):

Hourly Consulting:

The Project Engagement Invoice with Scope Documentation

Invoice Flow app documents of an HR consultant — a training program, a phased compliance audit on deposit, a paid fractional-HR retainer and a draft next phase
Training, a phased audit, the fractional retainer — every engagement type in one ledger.

Every project invoice now includes explicit scope documentation:

HR Consulting Project — [Company Name] — [Date]:

The “out of scope” line is as important as the “scope of work” section. It explicitly excludes things clients commonly assume are included — like legal review. No surprises, no disputes.

The Fractional HR Retainer Invoice

Monthly recurring invoice for fractional HR clients:

Fractional HR Services — [Company Name] — [Month Year]:

The hours-used summary attached to the invoice shows clients what their fractional HR retainer was spent on. It reinforces value and prevents the “what do I get for this?” question at renewal.

Corporate HR Project Invoices with PO Fields

Invoice Flow app recurring invoices of an HR consultant — a monthly fractional-HR retainer and a quarterly compliance review
The fractional retainer and quarterly review bill themselves — steady income, no admin.

Larger companies with HR departments or procurement teams require purchase order documentation:

HR Consulting Services — [Company Name] — [Date]:

Investigations and Compliance Support

Invoice Flow app invoice editor of an HR consultant — a 2-day leadership workshop, per-participant materials and facilitation travel with program and L&D code in custom fields
The workshop, per-head materials, travel — with the L&D code their budget team needs.

Workplace investigation work — harassment complaints, discrimination claims — requires careful invoice documentation for both HR and legal record purposes:

HR Investigation Services — [Company Name] — [Date]:

Investigations are billed hourly, not at project fee, because scope depends on what the investigation reveals.

Four Years of Independent HR Consulting

Current practice breakdown:

I have not had a scope dispute since I rebuilt the billing structure. The scope documentation on the invoice eliminated the ambiguity that created the original problem.

What InvoiceFlow Does for HR Consultants

HR consulting billing involves project invoices with explicit scope and out-of-scope documentation, fractional HR monthly retainers auto-generated with hours summary, corporate PO fields for large company clients, and investigation billing with confidentiality documentation. InvoiceFlow provides the structure for all of these from one Android app.

Download InvoiceFlow. Document scope explicitly on every project invoice — including what’s out of scope. Set up fractional HR retainers on recurring billing. The invoice is your scope agreement.

Michelle Park is an HR consultant in Seattle, Washington, providing fractional HR leadership, HR project consulting, workplace investigation, and HR strategy services to small and mid-size companies.