How to Build an Approval Workflow in Slack (And When to Switch to a Real Tool)
For a small enough team, Slack is your CRM, your project manager, your support desk, and yes — your approval workflow. There's nothing wrong with that. Until there is.
This guide walks through how to actually run approvals in Slack the right way, the predictable failure modes, and the clear signals it's time to graduate.
The Slack approval workflow that works (for now)
If you have under 5 people, a structured Slack-based approval flow can work. Here's the version we've seen survive the longest:
Step 1: One dedicated channel
Create #approvals or #purchases. Don't mix it with #general or #ops. Approvals need to be findable later.
Step 2: A required template
Pin a message at the top of the channel:
To request a purchase, post in this channel using this template:
- What: [item or service]
- Vendor: [where you're buying]
- Cost: [estimate]
- Why: [one sentence]
- Department: [team/project to charge]
Tag your manager with
@manager-name. Manager: react with ✅ to approve, ❌ to reject. After purchase, reply in thread with the receipt.
Step 3: Slack Workflow Builder for routing
Use Slack's Workflow Builder to create a form-based version of the template. Hit a shortcut, fill the form, it posts a structured message and pings the right person.
Step 4: Receipt requirement
Once approved, the asker must post the receipt as a reply in the same thread. This keeps the approval and receipt together — easier to find later.
Step 5: A monthly review
The owner (or bookkeeper) scrolls back through the channel once a month and exports approved items into a spreadsheet for the books.
That's it. It's the cleanest possible Slack-based approval workflow.
The 5 ways it predictably breaks
We've watched dozens of small businesses run this exact playbook. Here's how it dies, every time, in order of how soon each problem hits:
1. People stop using the template (week 2)
Someone posts "hey can I buy a $40 cable" without the template. You approve it because it's $40 and you're busy. Now everyone knows the template is optional. By week 4, half the requests are formless. By month 2, the channel is unparseable.
2. The receipt loop falls apart (month 1)
Receipts get attached "later." Then "I'll forward it." Then "I sent it to email." By month 3, you're missing 30% of receipts. By tax season, your bookkeeper is sending you a spreadsheet of $14,000 in undocumented spend.
3. Approvals happen verbally (month 2)
The asker DMs you instead of posting in the channel. Or they catch you in the kitchen and ask in person. You say "sure, just buy it." Now the approval doesn't exist anywhere. Three months later, when the bookkeeper asks about the charge, neither of you remembers.
4. The owner becomes a 24/7 approval bot (month 3)
Every $30 purchase pings you. Slack notifications go off during dinner, during family time, during important calls. You start ignoring them. Approvals back up. People start buying things and asking forgiveness instead.
5. New hires can't figure out the system (month 6)
A new hire joins. They don't know about the channel. They don't know who to tag. They DM their manager. Their manager forwards it to you. You approve via emoji. The receipt never gets attached. Multiply by every new hire.
When to switch — the 4 signals
If two or more of these are true, you've outgrown Slack:
Signal 1: Your team is over 5 people, OR you've added a new hire in the last 90 days who got confused about the process.
Signal 2: You're missing more than 10% of receipts at month-end (your bookkeeper will tell you the exact number — ask).
Signal 3: You're approving more than 5 purchases per week personally, and a third of them are under $100.
Signal 4: You can't find a specific past approval in under 30 seconds when an audit, finance question, or vendor dispute requires it.
If any of those describe you, the cost of staying on Slack now exceeds the cost of switching.
What to actually switch to
You have options:
Form-based workflow (Google Forms + Sheets + Zapier): Free, but painful to use, no notifications, no mobile, hard to report on. Buys you 6 months at most.
Dedicated approval software (Becision, Ramp, Airbase, etc.): Real tool, mobile-first, includes notifications, reporting, audit trail. Free for small teams. See our comparison of approval software.
Procurement suite (Procurify, Coupa): Overkill for small teams. Skip until you're 100+.
For most teams reading this, Becision is the closest replacement for "what we wish Slack approvals were." Same speed, same low friction — but with a real audit trail, mobile push notifications, and mandatory receipt capture. Try it free →
The honest "stay on Slack" advice
If you're under 5 people, work in person, and your spending is under $20K/year — stay on Slack. Just be honest about the failure modes above so you spot them early.
The wrong move is being a 25-person team still pretending Slack is enough. By the time you admit it, you've already burned a year of receipts, frustrated your bookkeeper, and lost real money to missing deductions.