Overlapping zipcodes: detect and resolve zones that share a zipcode

When you define delivery zones by zip/postal code, the same zipcode can accidentally end up in more than one zone. DingDoong now detects these overlaps for you and lets you decide what should happen — either pick one winning zone per zipcode, or let customers choose their zone at checkout.

Overview

If you run local delivery with multiple zones (for example "Inner city" and "Suburbs"), it's easy to list the same zipcode in two zones by mistake. When that happens, DingDoong doesn't know which zone — and which delivery rules and rates — should apply to a customer in that zipcode.

The overlap check looks across all your delivery zones, flags every zipcode that appears in more than one zone, and shows you exactly which zones share it. You then choose how overlaps behave: keep one zone per zipcode (recommended for clean rates), or allow the overlap and let the customer pick.

Before you start

• DingDoong is installed and your delivery widget is live on your store.
• Your delivery restriction is set to Postal/zip code match (the overlap check only applies to zip-code zones).
• You have at least two delivery zones with zip/postal codes entered.

How to find and resolve overlapping zipcodes

Here's how, step by step:

Step 1: Open your delivery zone settings

In the DingDoong admin, go to your Delivery settings and open a zone that uses Postal/zip code match. This is where your zip/postal codes for the zone are listed.

Step 2: Spot the flagged zipcodes

Any zipcode that also exists in another zone is marked with a ⚠️ warning icon in the zip-code list. Below the list you'll see a summary such as "3 zipcode(s) above also exist in 2 other zone(s)." Click Show which to expand the list and see the exact zone names and codes that overlap.

Step 3: Review the overlap in Delivery restriction

In the Delivery restriction card, when an overlap exists you'll see an Allow overlapping zipcodes toggle and a line like "2 overlapping zipcode group(s) across your zones." Click Show details to expand a banner for each overlapping group, listing the shared codes and the zones involved.

Step 4: Decide how the overlap should behave

Choose one of two options:

• Leave "Allow overlapping zipcodes" OFF (recommended): Each shared zipcode is delivered by only one zone — the top-ranked one. The banner shows a warning, and you must resolve it before saving (see Step 5).
• Turn "Allow overlapping zipcodes" ON: Customers whose zipcode sits in several zones pick their zone themselves at checkout. The banner turns informational and saving is no longer blocked.

Step 5: Set zone priority (or remove duplicates)

In each overlap banner, click Review zone priority (overlap off) or Reorder zones (overlap on) to open the priority modal. Drag zones up or down:

• With overlap off, the top zone gets a "Wins shared zipcodes" badge — it's the one that delivers to those customers; the others won't.
• With overlap on, the top zone gets a "Shown first" badge — this only controls the display order customers see; they still choose.

Click Save order. Alternatively, you can simply remove the duplicate zipcode from one of the zones to clear the conflict entirely.

Step 6: Save your settings

How it looks on the storefront

When Allow overlapping zipcodes is off, a customer entering a shared zipcode is matched to a single zone (the top-ranked one) and sees that zone's delivery options and rate — no duplicates.

When it's on, a customer in a shared zipcode is offered the matching zones to choose from, in the priority order you set, and they select the one they want before continuing.

Common scenarios

Two zones accidentally list the same zipcode

Open the priority modal, keep Allow overlapping zipcodes off, and either rank the correct zone to the top so it "wins", or remove the duplicate zipcode from the zone that shouldn't have it.

You intentionally want a zipcode in multiple zones (e.g. standard vs express)

Turn Allow overlapping zipcodes on so customers in that zipcode can choose between the zones (for example a cheaper standard zone and a faster express zone), then use Reorder zones to decide which one is shown first.

A zipcode sits in three or more zones

The overlap check groups all co-occurring zones together, so a 3-way (or larger) overlap appears as a single group. Resolve it the same way — rank them in the priority modal or trim the duplicates.

Configuration options

The overlap check understands more than plain numbers: it matches exact codes, partial/prefix codes, numeric ranges (e.g. 1000:2000), and UK postcodes, so a code is flagged even if two zones express it differently.

Tips & Best practices

Troubleshooting

I can't save my delivery settings — what's blocking it?

Some zipcodes belong to more than one zone while Allow overlapping zipcodes is off. Either turn the toggle on, or open the priority banner / zip-code list and remove the duplicates, then save again.

The warning icon stays on a zipcode after I edited a zone

The check reflects your unsaved edits live. If a code is still flagged, it genuinely still exists in another zone — expand Show which to find where, and remove or re-rank it.

I turned overlap on but customers still only see one zone

Make sure you saved the settings, and that the customer's zipcode actually falls into more than one zone. A zipcode only shows a choice when it's part of a detected overlap group.

FAQ

Does enabling the overlap check change my existing zones or orders?

No. Detection only surfaces conflicts and asks you to choose. Nothing changes until you save a priority order, toggle overlap, or remove a code.

How do I undo a change?

Turn Allow overlapping zipcodes back off (or on) to revert your choice, re-open the priority modal to restore the previous order, or re-add a zipcode you removed. Then save.

What decides which zone "wins" when overlap is off?

The top-ranked zone in the priority modal for that overlap group. Reorder it any time to change the winner.

Updated on: 24/06/2026