How you charge clients shapes everything else: how you estimate, how you track time, how you invoice and how much risk you carry. The three common models for agencies, consultancies and IT service companies are hourly billing, fixed price and retainer. Each has clear strengths — and each needs time tracking for a different reason.
Hourly billing
The client pays for every billable hour at an agreed rate.
- Good for: open-ended work, support, consulting, projects where scope will change.
- Pros: low risk for you; scope changes pay for themselves.
- Cons: clients may question hours; revenue depends on volume; efficiency isn’t rewarded.
- Time tracking is: the invoice. Accuracy and a clear breakdown per project or task matter most.
Fixed price
An agreed amount for a defined piece of work, regardless of the hours it takes.
- Good for: well-defined projects — a website, an implementation, a report.
- Pros: clients love predictability; you profit from working efficiently.
- Cons: you carry the risk of underestimating and of scope creep.
- Time tracking is: your early-warning system. You don’t bill the hours, but you must know whether they’re eating the margin.
Retainer
A recurring monthly fee, often including a number of hours, with extra hours billed on top.
- Good for: ongoing relationships — maintenance, marketing, fractional roles.
- Pros: predictable income; easier capacity planning.
- Cons: needs discipline to track included hours, or the retainer silently turns into unlimited work.
- Time tracking is: how you prove the value of the retainer and spot overages each month.
Side by side
| Hourly | Fixed price | Retainer | |
|---|---|---|---|
| Who carries the risk | Client | You | Shared |
| Revenue predictability | Low | Per project | High |
| Rewards efficiency | No | Yes | Partly |
| Key number to watch | Billable hours | Hours vs. budget | Hours vs. included hours |
Mixing models
Most companies use more than one model — hourly for one client, fixed price for another, retainer for a long-term partner. The important thing is that your tools know which is which.
In Clocknico you choose the billing method per client on the Billing page: hourly (with a client or employee rate), fixed amount, or retainer with included hours. Invoices and reports follow that choice, and the Profitability page calculates revenue accordingly — from billable hours for hourly clients, and from issued invoices for fixed-price and retainer clients.
Which one should you choose?
- If you can’t define the scope, bill hourly.
- If you can define the scope and you’ve done similar work before, consider fixed price — and track time to learn from every project.
- If the relationship is ongoing, propose a retainer and review the hours monthly.
Whatever you choose, track the time. It’s the only way to know whether the model is working. Clocknico is free for teams of up to 5 users, with billing and invoicing included.