Retainer Billing for Freelancers: Monthly Invoicing with Overage Hours

What is a retainer agreement?

A retainer is a standing agreement where a client pays you a fixed monthly fee in exchange for a guaranteed allocation of your time. The client gets priority access to your availability, and you get stable, recurring revenue.

For example: a marketing consultant might agree to a €2,000/month retainer that includes 20 hours of work. If the client needs more than 20 hours, the extra hours are billed at an agreed overage rate (e.g., €120/hour).

Retainers differ from project-based billing in a crucial way: you're selling your availability, not just deliverables. The client is paying for the certainty that you will be there when they need you, every month.

When to use retainers vs. project-based billing

Retainers aren't right for every client. Here's when they make sense:

Many freelancers use a mix: retainers for their core clients and project billing for one-off work. The retainer provides a stable income base while projects add upside.

Key terms to define in your retainer agreement

A retainer without clear terms leads to scope creep, billing disputes, and resentment on both sides. Define these in writing before you start:

• Monthly fee— the fixed amount the client pays each month, regardless of whether they use all hours (e.g., €2,000/month).
• Included hours— the number of hours covered by the monthly fee (e.g., 20 hours). This is the ceiling before overage kicks in.
• Overage rate— the hourly rate for time beyond the included hours (e.g., €120/hour). Typically higher than the effective hourly rate within the retainer to discourage overuse.
• Unused hours policy— what happens to hours the client doesn't use? Do they roll over, or reset to zero? (More on this below.)
• Billing cycle— when do you invoice? Start of month (prepaid), end of month (postpaid), or a specific date?
• Scope of work— what types of tasks are covered? Define boundaries to prevent scope creep (e.g., “Content writing and social media management. Website development is out of scope and billed separately.”).
• Notice period— how much notice is required to cancel or modify the retainer? 30 days is standard.

Setting up a retainer project in Bontello

Tracking retainer work requires linking time entries to a project and comparing them against your included hours. Here's how to set it up:

1. Go to Projects and create a new project for the retainer (e.g., “Acme Corp — Monthly Retainer”).
2. Set the project type to Retainer and enter the monthly fee, included hours, and overage rate.
3. Link the project to the client. This connects all time tracking, expenses, and invoices to the same account.
4. Start tracking time against this project using the timesheet. Each entry logs hours, a description, and the date.
5. At month-end, review the total hours worked. If hours are within the retainer limit, the invoice is simply the monthly fee. If hours exceed the limit, Bontello calculates the overage amount.

Monthly billing workflow

A consistent monthly process keeps your retainer billing smooth and professional:

Step 1: Review hours at month-end

Open the project and check total hours for the month. Compare against the included hours. Note any overage.

Step 2: Create the monthly invoice

Generate an invoice from the project. The base line item is the retainer fee. If there are overage hours, they appear as a second line item with the overage rate and hour count.

Step 3: Attach the time report

Send the invoice with a time summary showing what work was done, when, and for how many hours. Transparency builds trust and reduces payment disputes. You can export a time report from the timesheet.

Rollover vs. reset: choosing the right unused-hours policy

This is the most-debated aspect of retainer billing. What happens when a client uses only 12 of their 20 included hours in a month?

Reset (use it or lose it)

Unused hours expire at the end of the month. The client still pays the full retainer fee. Next month starts fresh at zero.

• Advantage: Simpler accounting, predictable workload for you.
• Advantage: No accumulation of “banked” hours that the client can dump on you at once.
• Disadvantage: Some clients feel they're losing value in quiet months.

Rollover (carry forward)

Unused hours roll into the next month. If the client uses 12 of 20 hours in March, they have 28 hours available in April (20 new + 8 carried over).

• Advantage: Clients feel they're getting fair value even in quiet months.
• Disadvantage: Hours can pile up, leading to a sudden burst of work you can't absorb.
• Tip: Cap rollover at 1 month (e.g., max 40 hours total). This prevents runaway accumulation.

Most experienced freelancers use reset— it's what the client is paying for: your guaranteed availability that month. If you choose rollover, always set a cap and put it in writing.

Key takeaways

• Retainers provide predictable monthly income in exchange for guaranteed availability.
• Define monthly fee, included hours, overage rate, and unused-hours policy in the agreement.
• Track all time against the retainer project — detailed records prevent disputes.
• Bill the base retainer fee plus any overage hours as separate line items on each invoice.
• Attach a time report to every monthly invoice for transparency.
• Reset (use-it-or-lose-it) is simpler and more common than rollover — if you rollover, cap it.
• Review and adjust retainer terms quarterly to match actual workload and evolving needs.