Parallel time tracking: billing multiple clients at once
Last updated: July 2026
Most time trackers assume one timer at a time, because most work is one thing at a time. But plenty of real work is not: an agent builds while you review someone else's pull request, an on-call retainer ticks along under your focused project, a long deploy runs while you start the next task. Parallel time tracking handles that honestly — but only if you follow a couple of rules that keep it from turning into double-billing. Here is when to use it, and how.
When one timer is not enough
A single running timer models a single stream of attention. Several situations genuinely break that model:
- On-call and retainers. You are contractually available to one client while doing focused work for another — both are legitimately "on the clock," differently.
- Background work you supervise. An AI agent, a long build or a deploy runs for one project while your active attention is on another.
- Genuine oversight. You are monitoring one engagement while progressing a second.
Forcing these into one timer means either stopping and starting constantly (and forgetting), or attributing time to the wrong client. A tracker that supports parallel timers lets each stream run on its own line.
The double-billing rule
Parallel timers come with one hard ethical line: do not charge the same minute of genuine, active effort to two clients at full rate. Two things can be true at once — a build runs for Client A while you actively code for Client B — and billing both can be defensible when each reflects a real, agreed basis (for example, an availability retainer plus focused work). What is not defensible is billing two clients your full hourly rate for the same hour of your undivided attention. The test is simple: could you justify each line to each client, out loud, at the same time? If not, split the time instead of overlapping it.
How parallel timers work in practice
Mechanically, it should be effortless. In Døgn you start a timer for one project, then start another without stopping the first; when two or more run, the popover groups them under "Running" and you end a specific one with "Stop this timer." Each becomes its own entry, attributed to its own client at its own rate. That way a two-hour window where you supervised one project and actively worked another produces two clean lines you can reason about — not one ambiguous block you have to reconstruct. See Tracking time for the step-by-step.
Overlap or split — choosing correctly
Two tools, two jobs. Overlap (parallel timers) is right when two distinct, separately justifiable things truly happen at once — focused work plus an availability retainer, say. Splitting is right when a single block of attention was shared between clients: divide the hour rather than charging it twice. A useful habit is to default to splitting and reserve overlap for cases where each client has an independent, agreed reason to be billed for that time. When in doubt, split — it is the conservative, trust-preserving choice, and it never puts you in the position of over-billing.
Keep each client on its own line
The whole point of tracking in parallel is clean attribution, and that only survives if each stream stays separate all the way to the invoice. Give every timer its own client and project so the hours roll up correctly; mark background or availability time with the right billable status; and review at week's end so overlaps are deliberate, not accidental. Then a month of concurrent work becomes a per-client report and a set of invoices, each defensible on its own. This is the same discipline consultants and agencies rely on daily — more in time tracking for consultants and agencies.
Questions, answered
Can I run two time trackers at the same time?
Yes, if your tracker supports parallel timers — start one for each concurrent stream and stop them independently. Døgn groups running timers under "Running" and lets you stop a specific one, so each concurrent project becomes its own entry attributed to its own client.
Is it ethical to bill two clients for the same time?
Only when each has an independent, agreed basis — for example an availability retainer running alongside focused work for another client. Billing two clients your full rate for the same hour of undivided attention is not defensible; when a single block of attention is shared, split the time instead.
When should I use parallel timers instead of one?
Use them when genuinely distinct streams run at once: an on-call retainer under focused work, or a background build, deploy or AI agent for one project while you actively work another. For a single shared block of attention, split the time rather than overlapping it.
How do I avoid double-billing with parallel tracking?
Apply one test: could you justify each line to each client out loud at the same time? Default to splitting shared attention, reserve overlap for separately agreed bases like retainers, and review your week so every overlap is deliberate. Keeping each timer on its own client and project keeps the record clean.