Exact Online Trello integration: stop sync loops fast

Exact Online–Trello integration without sync loops (implementation guide)

If you’re trying to keep Exact Online orders and Trello cards in sync in both directions, the biggest risk isn’t “can I connect them?”—it’s building a setup that doesn’t create duplicate records, overwrite newer changes, or loop endlessly.

This guide walks through a practical way to design a bidirectional sync using an automation layer (like Zapier or Make), including field mapping, loop prevention, conflict rules, and a phased rollout plan.

What you’re actually trying to automate

Most teams want something like this:

When a new order is created (or received) in Exact Online, create a corresponding Trello card.
As the order moves through departments, updates in either system (Exact Online or Trello) should reflect in the other.
The team stops doing “triple entry” (email + Trello + Exact Online) and can trust one workflow.

Step 1: Define the “source of truth” per field (don’t sync everything)

A bidirectional sync only works when you decide which system owns which fields.

Create a simple mapping table (even in a spreadsheet) and label each field as:

Exact-owned (Trello can display it, but shouldn’t write it)
Trello-owned (Exact can display it, but shouldn’t write it)
Shared (both can write it, but then you must have conflict rules)

Common safe defaults:

Exact-owned: order number, invoice/financial fields, customer record references
Trello-owned: internal checklist state, internal assignee, internal notes
Shared (only if needed): status, due date, “ready for next department” style flags

Step 2: Create stable record links (so updates don’t spawn duplicates)

To update records safely, each side needs a reliable “pointer” to the other.

Recommended pattern:

Store the Exact Online Order ID on the Trello card (e.g., in a custom field).
Store the Trello Card ID on the Exact Online record (if you have a place for a custom field / note / reference).

If you can’t store both directions, store at least one direction and also store a dedupe key (e.g., Order Number) so your automation can search before creating.

Step 3: Prevent sync loops (the #1 problem in bidirectional automation)

A sync loop is when:

Exact updates → automation writes to Trello → Trello update triggers automation → writes back to Exact → repeat.

Use one (or more) of these loop-prevention strategies:

Strategy A: “Last updated by integration” filter

If your tools expose “last updated by” metadata, filter triggers so that changes made by the integration user don’t trigger the reverse scenario.

Strategy B: Add a “Sync source” / “Updated by” marker field

Create a field that your automation sets when it writes an update.

Examples:

Last sync source = Exact or Last sync source = Trello
Last updated by automation = true

Then, in your triggers, add a guard like:

“Only run if last sync source is not the opposite system”

Strategy C: Use timestamps + a minimum delay window

For shared fields, compare last_modified_at timestamps.

A simple rule that prevents thrash:

If both sides changed within (say) 60–120 seconds, treat as a conflict and don’t auto-overwrite.

Step 4: Define conflict rules (what happens if both sides change?)

Conflicts are inevitable once you allow bidirectional updates.

Pick one approach:

Option 1: Exact wins for shared fields

Safer when Exact is the operational system.

Option 2: Trello wins for workflow fields

Safer when Trello drives internal execution.

Option 3: “Newest wins” with logging

Works when your data is clean and you can trust timestamps.

Always log what changed (even if it’s just a comment on the Trello card).

Step 5: Choose your automation layer: Zapier vs Make (for this pairing)

Both can work for Exact Online ↔ Trello. The decision usually comes down to complexity.

Zapier: faster to build, simpler maintenance, great when your mapping rules and conditions are straightforward.
Make: better for complex branching, advanced transforms, and more “engineering-style” workflows.

If you’re already feeling the workflow is “overwhelming,” start with Zapier and only move to Make if you actually hit a ceiling.

Step 6: Roll out in phases (so you don’t break operations)

A practical rollout plan:

Phase 1: Skeleton one-way flow (Exact → Trello)

New orders create cards
Minimal field mapping
No bidirectional updates yet

Phase 2: Add safe updates (Exact → Trello)

Update a limited set of fields
Keep Trello-owned fields out of scope

Phase 3: Add bidirectional updates for 1–2 shared fields

Add loop prevention + conflict rules
Monitor logs for a week

Phase 4 (optional): Historical / open-order migration

Most no-code automations run “from the day you turn them on.”

If you need existing open orders to appear in Trello, treat it as a separate migration job:

Export/search existing orders
Create matching Trello cards (dedupe-enabled)
Backfill IDs

Common pitfalls (and how to avoid them)

Duplicate cards: you didn’t store IDs or you didn’t search-before-create.
Endless updates: you don’t have a loop-prevention marker or integration-user filter.
Silent overwrites: you allowed shared fields with no conflict rules.
Too many fields too soon: start with a minimal mapping and expand only after it’s stable.

Get help designing the Exact Online ↔ Trello sync

If you want an expert to map fields, build the safeguards, and get a stable “skeleton” integration running fast, book a discovery call:

Book a free consulting call