Onboarding a new client splits the work across two companies.
On the agency side there's a contract to countersign, an invoice to send, a team to brief, and a kickoff to schedule. On the client side there's a different list: brand assets to dig up, GA4 and ad-account access to grant, a brief to read and approve.
Most onboarding delays come from that second list, because the client is busy, the access request is sitting in someone's inbox, and neither side is tracking it as an actual task with an owner and a date.
Agency client onboarding is also worth getting right for reasons beyond the schedule. In a survey of 330 executives by Harvard Business Review Analytic Services, more than 80% said a stronger focus on onboarding has a significant or moderate positive effect on revenue, renewals, and referrals over the life of the contract. The first weeks set the client's expectations for how organized the engagement will be.
What goes into agency client onboarding
The shape is similar whether you run paid media, SEO, design, or development. Between the signed contract and the first real deliverable, six things have to happen:
- Contract and payment setup.
- Internal team briefing. Context has to move from sales to delivery before the kickoff, and it's the same transfer problem covered in this guide to the sales-to-customer-success handoff in Slack.
- The kickoff call.
- Access, credentials, and assets.
- Communication cadence and points of contact.
- A first-30-days plan.
What makes this harder than a normal project is that the steps are owned by different people in two different companies, and each one can hold up the others.
Plan for the access step to take the longest
Collecting access is the step agencies most often underestimate. Take GA4 as the typical example: to add your agency's email to the property, the client needs someone with the Administrator role, per Google's access management docs.
The marketing manager you've been talking to often doesn't have that role and doesn't know who does. So the request gets forwarded, sits for a few days, comes back with Viewer access when you asked for Editor, and you start the loop again. Multiply that by the ad accounts, the CMS, the social profiles, and a brand folder that lives on someone's laptop.
First, send every access request on day one, together, with exact instructions per platform — which email to add, which role to grant, a screenshot of where the setting lives. Don't wait until the week you need each account.
Second, make each request a tracked item with a named owner on the client side and a date, rather than a paragraph in a long email, so there's something concrete to follow up on when it stalls.
Track Onboarding
Onboarding is a small project with two companies in it, so it needs a home:
- Your project management tool, with client guest access. Asana, ClickUp, and Monday all support guest seats.
- A Notion page or client portal. A welcome page with the timeline, links, and FAQ.
- Email plus a shared spreadsheet. Zero setup and every client can use it.
- A shared Slack channel with the client. If the client's company uses Slack, you can open a channel between the two workspaces with Slack Connect and run onboarding in it. There's no portal to issue credentials for and no second tool for the client to adopt.
The channel question matters more than it looks, because a new client will default to answering wherever is convenient: a reply to the welcome email, a DM to the account lead, a comment on a call.
Agreeing on one channel at kickoff — and putting the tasks in that same channel — removes that copying job entirely. That's the argument for the Slack option when the client is on Slack already.
Running onboarding in a shared Slack channel
The setup is one channel per client, something like #acme-x-youragency, opened via Slack Connect so people from both companies are in it. Conversation, files, and approvals happen there, and each onboarding step lives in its own thread in the channel.
Chaser is the Slack extension that allows tracking tasks in Slack. You can assign a task to your own staff or to the client's contact the same way in a Slack Connect channel:
- "Grant GA4 access" gets assigned to the client's marketing manager with a due date;
- "Internal team briefing" gets assigned to your account lead.
If an assignee doesn't acknowledge a task, Chaser sends them a quiet DM; if a task goes overdue, it posts a reminder in the task's thread.
Client-side people don't need an account set up, and per Chaser's pricing, people you work with through Slack Connect are free — and they only ever see their own channel, never your other clients or your internal work.
Since onboarding follows the same steps for every client, it's a natural fit for a reusable checklist. With Chaser you build the sequence once, with a {Client} placeholder so "Collect brand assets" becomes "Acme Corp — Collect brand assets" when you run it, and with deadlines set relative to a key date.
If onboarding is delayed after you’ve run the checklist, move one task’s due date. You can then shift the rest of that run by the same amount with just a click.
This guide to Chaser templates in Slack walks through building one. Steps the client shouldn't see, like the internal briefing or pipeline notes from sales, can run as a separate checklist in your internal channel.
Chaser posts an automatic status report to the channel on a schedule you pick, listing what's done, what's in progress, and what's waiting — including what's waiting on the client.
When the client can see that three of the four open items are theirs, the follow-up conversation tends to take care of itself.
