If you work with the same clients month after month, invoicing project by project creates unnecessary admin and unpredictable cash flow. Recurring invoices and retainers fix both: the client pays a regular, agreed amount on a regular schedule, and you spend less time chasing and estimating. This guide explains the different models, how to set them up and how to invoice them cleanly.
Recurring invoice vs. retainer
The two are related but not the same:
- A recurring invoice is any invoice issued on a regular schedule for the same (or similar) amount — a monthly maintenance fee, a subscription, rent, a fixed bookkeeping fee.
- A retainer is an agreement where a client pays in advance for access to your time, availability or a defined set of deliverables over a period. Retainers are usually billed with recurring invoices.
Common retainer models
| Model | How it works | Best for | Watch out for |
|---|---|---|---|
| Fixed-hours retainer | Client buys e.g. 20 hours/month at a set price | Design, development, marketing support | Unused hours and overages need clear rules |
| Fixed-deliverables retainer | Set outputs per month (e.g. 4 blog posts + 1 newsletter) | Content, social media, reporting | Scope creep — define each deliverable |
| Access / availability retainer | Client pays to have you on call, with or without a time allowance | Legal, consulting, technical support | Clarify response times and what’s included |
| Pay-in-advance deposit | Client prepays a balance; you draw down against it and top up | Agencies, lawyers, project-based work | Track the balance carefully; refund rules |
| Fixed recurring fee | Same fee for an ongoing service | Maintenance, hosting, bookkeeping | Review pricing annually |
What to put in the retainer agreement
Before the first invoice, agree in writing:
- Fee and period: “£2,000 per calendar month.”
- What’s included: hours, deliverables, response times, channels.
- Billing timing: in advance (start of the period) or in arrears (end of the period). Billing in advance is usual for retainers and much better for your cash flow.
- Payment terms: e.g. due within 7 days of the invoice date. See payment terms explained.
- Unused time: does it expire, roll over (and for how long), or get credited?
- Overages: what happens if the client needs more — e.g. extra hours billed at £100/hour in arrears, with approval above a certain number.
- Minimum term and notice: e.g. 3-month minimum, 30 days’ notice to end.
- Price reviews: e.g. annually, with 60 days’ notice.
How to invoice a retainer
Each recurring invoice is still a normal invoice: it needs its own unique number, dates, client details and tax. See what to include on an invoice. What’s different is that you should always state the period covered.
Example: monthly retainer invoice, billed in advance
| Description | Qty | Rate | Total |
|---|---|---|---|
| Marketing retainer — November 2026 (up to 20 hours) | 1 | £2,000.00 | £2,000.00 |
| Additional hours — October 2026 (approved 22 Oct) | 3 | £100.00 | £300.00 |
| Subtotal | £2,300.00 | ||
| VAT 20% | £460.00 | ||
| Total due | £2,760.00 |
Invoice date: 1 Nov 2026 · Due: 8 Nov 2026 · Service period: 1–30 Nov 2026. Retainer hours used in October: 23 of 20 (3 additional hours billed above).
Notice how this invoice bills this month’s retainer in advance and last month’s overage in arrears. That combination keeps the base fee predictable while still capturing extra work.
Include a short usage summary
Clients renew retainers when they can see the value. A brief summary of last period’s activity — on the invoice, in the email or as an attached report — helps:
October summary: 20 retainer hours + 3 approved extra hours. Delivered: 4 blog posts, October newsletter, Google Ads optimisation, monthly report.
Numbering recurring invoices
Recurring invoices use your normal invoice sequence — don’t reuse a number each month or give recurring invoices a special series unless your local rules allow it and you keep it unique. A typical pattern: INV-2026-0101 (October), INV-2026-0118 (November) — whatever the next number is. See invoice numbering.
Recurring invoices without a retainer
Many businesses simply bill the same service repeatedly: monthly bookkeeping, website maintenance, equipment rental, lessons, cleaning. The same principles apply:
- Invoice on the same day each period so clients come to expect it.
- Keep the description consistent but update the period.
- Mention any price changes in advance, not on the invoice itself.
- Consider automatic payment methods (direct debit, card on file, standing order) where your clients and payment provider support them — the biggest single improvement to recurring cash flow.
Prepaid balances: drawing down a deposit
For a pay-in-advance balance, show the running balance on every invoice:
| Item | Amount |
|---|---|
| Opening balance (prepaid) | $5,000.00 |
| Work this month: 18 hours at $150 | −$2,700.00 |
| Remaining balance | $2,300.00 |
| Top-up requested to restore $5,000 balance | $2,700.00 |
How you treat prepayments for tax and revenue recognition depends on your country and accounting method. For example, in VAT systems a prepayment can create a tax point when it is received. Check with your accountant.
Handling changes and cancellations
- Pausing: agree in writing what happens to the retainer fee during a pause.
- Ending: issue the final invoice for the notice period and any outstanding overages.
- Refunding unused prepaid amounts: if your agreement provides for a refund or credit, issue a credit note against the relevant invoice rather than editing it.
- Late payment on a retainer: pause work after a clearly stated period, and use our late payment reminder templates.
Pros and cons
| Pros | Cons |
|---|---|
| Predictable income and cash flow | You must deliver consistently every month |
| Paid in advance — less chasing | Unused hours can cause friction if rules are vague |
| Less time spent quoting and invoicing | Long notice periods may scare off some clients |
| Deeper client relationships | Easy to under-price if scope creeps |
Checklist
- Written agreement covering fee, scope, timing, overages, unused time and notice
- Invoices issued on the same day each period, billed in advance
- Every invoice states the service period
- Overages listed separately, with approvals referenced
- Each invoice has a new, unique number
- Usage summary shared regularly
- Price review date in the calendar
You can create each month’s invoice in a minute with the invoice generator — and BillKit Pro can save clients and line items so recurring invoices take even less time. For more cash-flow tactics, read how to get paid faster.
Tax and revenue-recognition rules for prepayments and retainers vary by country. This guide is general information, not legal, tax or accounting advice.