Who can set up a retainer?

Admins and managers. They also see the project's Billing tab and get the usage alerts. Other team members track time as usual.

Can I change the hours or fee partway through?

Yes. Edit the retainer in the project's settings. New hours and fees apply from the next period, so the current period keeps what the client already agreed to.

What if time is logged against a period that has already closed?

A closed period doesn't change. Correct the current period with Adjust hours and give a reason.

Is retainer time ever billed again on an hourly invoice?

No. Hourly invoices leave out time a retainer covers. Work in categories the retainer doesn't cover, and after-hours time you chose to bill separately, still goes on hourly invoices.

Does rounding change the time my team logged?

No. Rounding changes billing figures only: invoice lines, retainer usage and unbilled amounts. Timers, timesheets and time spent keep the exact time.

Can I sell a block of hours instead of a monthly plan?

Yes. Choose Whole term as the billing period and set an end date. The client gets one allowance and one fee for the whole contract.

Set up a client retainer

A retainer sells a client a set number of hours each month, quarter or year, or for the length of a contract, for a fixed fee. Zentract counts the time your team logs against those hours, tells you as they run low, and invoices the fee and any overage. This guide sets one up from the start, using a monthly website care plan as the example.

Before you start: how time bills

Two organization settings shape every retainer. Set them once in Organization settings, under Time billing.

Time billing settings: entries round up to 15 minutes with a 15 minute minimum and a 1.5 after-hours multiplier, and three work categories: Maintenance, New development and Support. — Rounding and the after-hours multiplier apply to every project unless the project overrides them.

Choose how time rounds
Round each entry to an increment, such as up to the next 15 minutes, and set a minimum per entry if you charge one. Rounding applies to retainer usage and hourly invoices alike.
Set the after-hours multiplier
Time outside your business hours can bill at a higher rate, such as 1.5×. Set your hours under Business hours in the same settings. Leave the multiplier at 1 if you don't charge extra.
Add work categories
Categories such as Support, Maintenance and New development let a retainer cover some work and not others. Skip them if the retainer covers everything you do for the client.

Work the retainer doesn't cover bills hourly at your team's rates. Set each person's rate under Team, or give the project its own rates on its Team rates tab.

Add the client and their project

Add the client
In Clients, choose New client and enter their name and billing email. Add their tax details if you invoice with tax.
Create the project
Open the client and choose New project. Pick the currency you'll invoice the retainer in. A retainer belongs to one project, so create a project for each agreement.

Set up the retainer

Open the project and go to its Billing tab. A project without a retainer bills hourly. Choose Set up retainer.

The project's Billing tab says the project bills hourly, with a Set up retainer button.

Term, hours and fee

Retainer term settings: monthly billing period, doesn't renew, starting October 1, 2026, with 20 hours and a 1,500 fee per period invoiced at the start of each period. — A monthly retainer of 20 hours for 1,500, invoiced at the start of each month.

Billing period: Monthly, quarterly or annual repeats the hours and fee each period. Whole term gives one allowance and fee for the contract and needs an end date.
Start date: Periods start on this day. A retainer starting on the 15th runs from the 15th to the 14th.
End date and renewal: Leave the end date empty for a retainer that runs until you end it. With an end date, choose whether it renews automatically on the same terms or you renew it yourself. To renew, open the project's Billing tab and choose Renew. The new term starts the day after this one ends, with the same terms unless you change the hours, fee, overage rate, end date, renewal or notes. Zentract reminds you 14 days before a manual renewal is due and again on the last day.
Hours and fee: The hours included each period and the fee for them. Invoice the fee at the start of each period, or when it closes.

Overage, after-hours and unused hours

Overage billed at 95 an hour, after-hours work counted at the after-hours multiplier, and unused hours rolling over, at most 10 hours, expiring after 2 periods.

When a period goes over: Bill overage at the overage rate when the period closes, deduct it from the next period's hours, or don't bill it. Don't bill overage still records it, so you can see when the plan is too small.
After-hours work: Count it like other hours, count it at the after-hours multiplier (1.5 hours used for each hour worked at 1.5×), or leave it out of the retainer and bill it separately at the after-hours rate.
Unused hours: Let them expire, or roll them over to the next period. Cap how many roll over and how many periods they last. Rolled-over hours are used first.

Covered work

Check the categories the retainer covers, or leave them all unchecked to cover everything. Tasks without a category always count against the retainer. Only billable tasks count.

Finally, set when admins and managers are alerted, by default at 80% and 100% of the period's hours, and note the terms of the agreement. Choose Create retainer.

Give tasks a category

When the retainer covers some categories and not others, set the category on each task. Time logged on the task follows it.

A task's details, with Category set to Support.

Each period

The project's Billing tab shows the current period: the hours available, used and remaining, and the fee and overage it can invoice.

Current period, October 1 to 31, 2026: 20 hours available, 12.5 used and 7.5 remaining. The 1,500 fee has a Create invoice button, and overage is settled at close.

Create invoice: Drafts an invoice for the period's fee, or its overage once the period has closed. Each charge is invoiced once.
Adjust hours: Adds or removes hours in the current period, with a reason. Use it for goodwill hours or to correct a closed period.
Share statement: Sends the client a link to the period's hours: what was included, what was used, and the work it went on. Add a password or an expiry if you like.
When the period closes: Zentract records the final usage, settles overage as you chose, rolls over or expires unused hours, and opens the next period. Closed periods are listed under Past periods.

See where the client stands

The client's page sums up all their projects: what they owe, what's unbilled, and how many retainers are running. Each project shows its hours used against the allowance.

Client page for Harbour Coffee Co.: nothing outstanding, 440 unbilled and 1 active retainer. The Website care plan project has used 12.5 of 20 hours. — The 440 unbilled is new development work, which the retainer doesn't cover.

Questions

Who can set up a retainer?: Admins and managers. They also see the project's Billing tab and get the usage alerts. Other team members track time as usual.
Can I change the hours or fee partway through?: Yes. Edit the retainer in the project's settings. New hours and fees apply from the next period, so the current period keeps what the client already agreed to.
What if time is logged against a period that has already closed?: A closed period doesn't change. Correct the current period with Adjust hours and give a reason.
Is retainer time ever billed again on an hourly invoice?: No. Hourly invoices leave out time a retainer covers. Work in categories the retainer doesn't cover, and after-hours time you chose to bill separately, still goes on hourly invoices.
Does rounding change the time my team logged?: No. Rounding changes billing figures only: invoice lines, retainer usage and unbilled amounts. Timers, timesheets and time spent keep the exact time.
Can I sell a block of hours instead of a monthly plan?: Yes. Choose Whole term as the billing period and set an end date. The client gets one allowance and one fee for the whole contract.