HubSpot deduplicates contacts using email by default, so a phone-first, referral-based, or high-touch sales business with no reliable email data ends up with duplicate leads piling up fast. Amwhiz fixed this for a client through its HubSpot consulting services by creating a custom "unique value" property, migrating phone numbers into it, and letting HubSpot enforce one record per number. Here's exactly how it was built.
HubSpot deduplicates contacts using email by default. If your leads don't reliably provide email (phone-first, referral-based, or high-touch sales businesses), duplicates pile up fast. The fix is to create a custom "unique value" property, migrate phone numbers into it, and let HubSpot enforce one record per number.
HubSpot's built-in deduplication is built around one assumption: every lead has an email address, and gives it up easily. For a lot of businesses, that's true. It wasn't true for us.
We work with high-value, high-touch clients who call, text, or come in through a referral and expect a phone call back, not a drip campaign. Email is often an afterthought. Sometimes it doesn't exist in the CRM at all. We ran into a related version of this problem on the Zoho side too, see the Apollo.io + Zoho CRM duplicate-safe lead engine case study for how the same principle applied there.
That's a problem, because HubSpot has no native protection against duplicates without an email address. Every time a lead came in through a different channel, campaign, or sales rep, a brand new contact record got created. The same person ended up split into two, three, sometimes four separate records scattered across the CRM.
Multiplied across thousands of contacts, the CRM stopped being a source of truth and started being a mess.
Duplicate contact records aren't just a cleanup chore. They quietly break things downstream:
For a business built on trust and high-touch relationships, this isn't a minor inefficiency. It's a credibility problem disguised as a data problem.
Instead of forcing email into a role it can't fill, we made phone number the unique identifier in HubSpot by creating a dedicated custom property with "Require unique values" enabled.
This didn't need an expensive data platform or months of "digital transformation." It needed one question answered honestly: what actually makes a lead unique in this business? For us, it was the phone number, the one detail nearly every lead provides regardless of how they enter the funnel. This is the kind of configuration work that's typically scoped as part of a broader HubSpot consulting engagement, alongside pipeline setup and lifecycle stage design.
Here's what we built:
The result: a CRM that identifies who its leads actually are, without needing a single email address to do it.
The slow leak of duplicate contacts is effectively sealed. Every new lead is checked against one non-negotiable rule: a phone number belongs to exactly one record, forever.
That means:
It's a small structural change with an outsized impact. It doesn't show up on a flashy dashboard, but it shows up everywhere else in the business.
Amwhiz scopes this kind of deduplication fix as part of every HubSpot consulting engagement, custom property design, data migration, and the rest of pipeline configuration, delivered as one itemized plan rather than a vague hourly tab. For businesses syncing HubSpot with another system, this same unique-identifier logic often gets built into the HubSpot custom integration work itself. Visit amwhiz.com or email sales@amwhiz.com to get started.
HubSpot's native deduplication engine uses email as the default unique identifier. If a contact record has no email, HubSpot has no built-in way to detect that it's a duplicate of an existing contact.
Yes. Create a custom contact property, enable "Require unique values" on it, and migrate existing phone numbers into it. HubSpot will then block any new or existing record from sharing that number.
Duplicates usually happen when leads enter through multiple channels (calls, referrals, forms, different sales reps) and the CRM has no reliable identifier, like email, to match them against existing records.
Yes. The same approach (a custom property with "Require unique values" enabled) works for any consistently collected field, such as an account ID or membership number, not just phone numbers.
The biggest wins in CRM management aren't always about turning on more automation or buying more tools. Sometimes it's asking one blunt question, what does "unique" actually mean for the humans in this database, and building the system around the honest answer instead of the convenient one.