Retainer and Recurring Invoices: How to Bill Monthly Clients
Recurring work should mean recurring, predictable income. That depends on invoicing the same way, on the same day, every month.
A retainer or recurring service (monthly bookkeeping, website care, social media management, cleaning, IT support) is the most valuable kind of client you can have. The invoicing is simple, as long as the rules are set once and followed every month.
Retainer vs recurring invoice
- Retainer: the client pays a fixed amount for your availability or a set amount of work (e.g. "up to 10 hours a month"). Common for consultants, lawyers, marketers and agencies.
- Recurring service invoice: the client pays for a defined ongoing service (e.g. "weekly office cleaning", "monthly payroll for up to 10 staff").
- Subscription: a fixed recurring charge for access to a product or service, often billed automatically.
On the invoice, they all look similar.
In advance or in arrears?
In advance (bill on the 1st for that month): standard for retainers. You're paid before you work, and the client is committed.
In arrears (bill at the end for work done): more common for variable recurring services and for clients who insist on it.
If you can, bill retainers in advance. It removes most of the cash flow risk.
What to put on the invoice
Marketing retainer, October 2026 Social media management (3 platforms), monthly content calendar, reporting. Up to 15 hours. Per agreement dated 12 March 2026. $1,800.00
Include:
- The period covered ("October 2026" or "1–31 October 2026")
- What the retainer covers, briefly, or a reference to the agreement
- Any extras beyond the retainer as separate lines
- The same invoice layout and wording every month
With overage
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Support retainer, September 2026 (10 hours included) | 1 | $900.00 | $900.00 |
| Additional hours beyond retainer (see log) | 3.5 | $95.00 | $332.50 |
| Total | $1,232.50 |
Unused hours: decide up front
Options, from most to least common:
- Use it or lose it: unused hours don't carry over. Simple, and standard for availability-based retainers.
- Limited rollover: unused hours carry over for one month only.
- Banked hours: hours accumulate, sometimes with an expiry.
Put the rule in the agreement. If you're generous one month, say so on the invoice ("2 unused hours rolled into October as a courtesy") so it doesn't become an expectation.
Keep it routine
- Same day each month. The 1st for advance billing; the last working day for arrears.
- Same number format. Sequential invoice numbers, even for recurring invoices; don't reuse a number each month. See invoice numbering.
- Same description, with only the month and extras changing.
With the generator, keep a saved copy for each retainer client. Each month: open the copy, change the date and period, download. Your details, the client and the line items are already there. "Start the next invoice" bumps the number for you.
Set up your retainer invoice once, save a copy, and reuse it every month.
Open the invoice generatorAutomating it
If you have several recurring clients, invoicing software that sends recurring invoices automatically (and charges a card on file or collects by direct debit) can be worth the subscription. See templates vs invoicing software.
Raising retainer fees
Review annually. Give 30–60 days' notice in writing, state the new fee and the date it applies from, and let the first invoice at the new rate speak for itself. A short note on that invoice ("New rate from 1 January, as agreed on 15 November") helps AP teams who didn't see the email.
Ending a retainer
Your agreement should say how much notice either side gives (30 days is common) and what happens to the final month's fee. Issue the final invoice as normal, and if you billed in advance for a period you won't work, issue a credit note or refund as agreed.
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