Guide to Retainer Invoicing (Structure, Scope, and Overages)

Retainer invoicing is how you bill a client a set fee, each period, for ongoing work or reserved time. Each retainer invoice should show the period it covers, the fee, what the fee includes, and any extra work billed in addition, such as overage hours. Write the rules for unused hours, overages and price changes into the contract first, then make every invoice follow them.

1. Choose the retainer type

The type decides what each invoice has to show:

• Access retainer: the client pays to have you available, such as a set response time, whatever the amount of work.
• Hours retainer: the fee includes a set number of hours each period, and extra hours are billed separately.
• Deliverables retainer: the fee covers set outputs each period, such as four blog posts a month.
• Hybrid: a base fee plus a small pool of hours.

Use one type for each client. A hybrid needs the clearest invoice, because the client has to see both parts.

2. Write the rules into the contract

Before the first invoice, the contract should set out:

• The fee and the billing frequency, such as monthly.
• What the fee includes: the hours, deliverables or availability.
• The overage rate for work beyond what's included.
• Unused hours: whether they expire or roll over, and if they roll over, the cap and how long they last.
• Price changes: how much notice you give and when a new fee takes effect.
• Ending the retainer: the notice period, the final invoice, and what happens to any prepaid period not used.

Ask a lawyer where needed. For the main contract terms, see freelance contract essentials.

3. Decide when to invoice

• In advance: you invoice at the start of the period, so the client pays before the work. Overage hours aren't known yet, so you bill them on the next invoice.
• In arrears: you invoice at the end of the period, for the fee plus any overage, once the work is done.

If you're paid in advance, the money isn't earned until you do the work. The open textbook Principles of Accounting, Volume 1 from OpenStax defines unearned revenue as an "advance payment for a product or service that has yet to be provided by the company; the transaction is a liability until the product or service is provided" (OpenStax, chapter 3 key terms, opened October 29, 2026). Ask your accountant how to record retainer payments. See what is deferred revenue.

4. What to put on each retainer invoice

• The service period, such as June 1 to June 30.
• The retainer name used in the contract.
• The fee as one line.
• A short summary of what's included.
• Overage lines, each with the hours, the rate and the period they relate to.
• The hours summary, for hours retainers: hours available, used, rolled over and expired.
• The due date and payment terms.

Give every invoice its own invoice number, including separate invoices for overages.

5. Keep the client informed between invoices

For an hours retainer, tell the client when they're close to using the included hours, before an overage invoice arrives. For example, send a short note when 75% of the hours are used. If the client keeps using far more or far fewer hours than the retainer includes, discuss changing the retainer or moving the work to a project. See how to handle scope creep.

Sample: an hours retainer with rollover and overage

This is a sample with invented figures. A designer's retainer is $3,000.00 a month for 20 hours, invoiced in advance on the 1st. Extra hours cost $160.00 an hour, billed on the next invoice. Up to 5 unused hours roll over into the next month only, and rolled-over hours are used first.

April

• Hours available: 20
• Hours used: 16
• Unused: 20 − 16 = 4, all of which roll over (under the 5-hour cap)

May

• Hours available: 20 + 4 rolled over = 24
• Hours used: 27
• Overage: 27 − 24 = 3 hours × $160.00 = $480.00

Invoice dated June 1

• June retainer (June 1 to June 30, 20 hours): $3,000.00
• May overage (3 hours × $160.00): $480.00
• Total: $3,000.00 + $480.00 = $3,480.00

The hours summary on the June invoice shows May's 24 hours available, 27 used, 0 rolled over and 3 billed as overage.

Where Billed fits

Billed's recurring invoices page says: "Establish a stable cash flow with retainers. Negotiating fixed prices and sending recurring invoices makes it easier for you to forecast your income and upcoming workload." It also says:

• "Choose whether to send invoices daily, weekly, monthly or yearly."
• "Auto send invoices or save them as draft to recheck and send later."
• "Billed creates a recurring profile for your customer and keeps all the payments and invoices related to that profile in one place."
• "Your clients can also link their credit cards which makes it easier for them to pay."
• In its FAQ: "Yes you can charge your clients and collect payments automatically by integrating Billed with Stripe."

In the sample, the $480.00 overage would go on the invoice as its own line.

Related Articles

• Recurring Invoices Guide
• How to Build Freelance Retainer Clients
• Guide to Hourly Invoicing
• What Is Deferred Revenue?
• How to Invoice for Freelance Work

Frequently Asked Questions

Should retainer invoices be sent at the start or the end of the month?

Either works if the contract says which. Invoicing in advance means the client pays before the work, and any overage is billed on the next invoice. Invoicing in arrears means you bill the fee and any overage together once the period is over.

What happens to unused retainer hours?

Whatever the contract says. Unused hours can expire at the end of each period or roll over, and if they roll over, the contract should set a cap and a time limit. In the sample on this page, up to 5 unused hours roll over into the next month only.

How do I bill overage hours on a retainer?

Add a separate line for the extra hours, showing the hours, the rate and the period they relate to. In the sample on this page, 3 overage hours at $160.00 add $480.00 to a $3,000.00 retainer invoice, for a total of $3,480.00.

Is a retainer paid in advance counted as income right away?

OpenStax describes an advance payment for a service not yet provided as unearned revenue, which is a liability until the service is provided. Ask your accountant how to record retainer payments.