How to Manage Monthly Retainer Invoices

What's a Retainer?

A retainer is a fixed monthly fee for ongoing services. You invoice £2,000/month, the client pays that amount every month, and you deliver a set amount of work.

Retainer Invoice Format

RETAINER INVOICE

Client: ABC Marketing Ltd
Period: May 2026

Monthly Retainer: £3,000
Includes:
- 40 hours consulting time
- 4 strategy sessions
- Monthly reporting
- Email support

Invoice Number: RET-0045
Date: 1 May 2026
Due: 15 May 2026 (Net 14)

Payment Terms: Monthly, in advance

Key Points

• Include what's covered: "40 hours," "10 blog posts," etc.
• Invoice on the same day each month: 1st or 15th for consistency
• State payment terms: "Due in advance" (collect before delivering) or "Due within 14 days" (collect after)
• Clarify overage: "Additional hours billed at £75/hour"
• Use sequential numbers: RET-001, RET-002, etc.

Best Practices

• Monthly statement: Attach report showing hours/deliverables used
• Annual review: Review retainer value at year end
• Advance notice: Warn client 30 days before renewal if planning price increase
• Auto-invoice: Use invoicing software to automate monthly sends

FAQ

What if client doesn't use all their hours?

Unused hours typically don't roll over (unless your contract states otherwise). Standard: "Use it or lose it" monthly.

Can I increase the retainer price mid-contract?

Only if your contract allows it or with mutual agreement. Most contracts allow 10% annual increase with 30 days' notice.