Duplicates in HubSpot are almost never the result of one thing going wrong. They accumulate over time, from multiple directions, and by the time someone decides to fix them the problem has usually been compounding for months or years.
Understanding where duplicates come from matters because a one-time cleanup only solves half the problem. If the sources are still active, the duplicates will return. This post covers the most common causes: what creates them, why HubSpot does not catch them automatically, and what you can do about each one.
1. Form submissions with different email addresses
This is the single most obvious source of duplicate contacts in HubSpot.
HubSpot identifies contacts primarily by email address. When someone submits a form using a different email than the one already on their record (a personal address instead of a work one, a typo, a role-based address like info@) HubSpot creates a new contact rather than updating the existing one.
The same person can exist in your portal a dozen times across a multi-year relationship with your company: the email they used to download a whitepaper in 2021, the work address they gave at a conference in 2023, the Gmail they used to register for a webinar last month. Each submission looks like a clean record to HubSpot. From a data quality perspective, it is three duplicates of the same person. This is hard to prevent entirely at the form level, because you cannot always force someone to use a consistent email address.
2. List imports
CSV imports are one of the most controllable duplicate sources, but also one of the most frequently mishandled.
When a marketing team imports a list from a trade show, event registration, or purchased data source, the import process asks whether to update existing records or create new ones. If "create new" is selected, or if the matching logic does not catch all the existing records, duplicates are created for everyone on the list who was already in HubSpot.
Imports also inherit whatever duplication existed in the source file. A list downloaded from an event platform may already contain the same person twice, with different email formats or one entry with a company suffix and one without. Both go into HubSpot as separate records.
3. Data enrichment and outbound tools
Apollo, Clay, Clearbit, ZoomInfo, and similar tools are among the fastest-growing sources of new duplicate records in HubSpot.
The problem is structural. Enrichment tools build contact and company lists independently of your existing CRM data. When they push records into HubSpot, they typically check for an exact email match to avoid creating duplicates. But an exact email match is a narrow check. If the person already exists in your portal under a slightly different email, a former company address, or no email at all, the enrichment tool creates a new record.
Run Apollo against a list of 500 target accounts. If 15% of those contacts already exist in your HubSpot under different emails, you have just added 75 duplicates. Run it again next quarter against a refreshed list, and the number compounds.
Clay is particularly active here because its workflows tend to run continuously rather than as one-off imports. Every enrichment pass is a potential duplicate creation event if there is no deduplication step in the workflow.
4. CRM migrations
Migrating to HubSpot from Salesforce, Dynamics, or another CRM is one of the highest-risk moments for data quality.
The source system almost always contains some level of duplication: records that were never cleaned, contacts merged in one system but not another, data imported from a legacy tool years ago. When that data is imported into HubSpot, the duplicates come with it.
What makes migrations particularly problematic is the timing. A migration import is often a large, one-time push of thousands of records. By the time duplicates are noticed — usually when someone tries to run a report or launch a campaign — the data has already been sitting in HubSpot for weeks, been updated, been associated with new activity, and in some cases been further duplicated by integration or import tools running on top of it.
Deduplicating before a migration is significantly easier than deduplicating after. The records are still in a contained system, the data has not diverged, and there is no HubSpot activity to reconcile. If you are planning a migration and have not run a deduplication pass on the source data yet, do it before you import.
5. Salesforce integration sync
If your HubSpot portal is connected to Salesforce, the integration is likely one of your most active duplicate generators.
The sync works by matching records between the two systems on a defined property, usually email. But Salesforce and HubSpot often hold different versions of the same contact: different email formats, different name capitalisations, records created at different times with slightly different data. When the sync cannot find a confident match, it may create a new HubSpot record rather than update an existing one.
The result is a pattern many teams discover only after the damage has accumulated. The integration has been running for six months, and there are now two or three HubSpot records for every major account: one from before the integration was set up, one created by the first sync, and sometimes a third from a subsequent sync after the contact's details were updated in Salesforce.
This is compounded by the fact that HubSpot's native merge button is disabled when the Salesforce integration is active. The duplicates created by the sync are also the hardest ones to clean up through standard HubSpot tooling.
6. Integrations without dedup logic
Beyond Salesforce and enrichment tools, any integration that creates HubSpot records can be a duplicate source if it does not include deduplication logic.
Phone and calling integrations — Aircall, Dialpad, CallRail, RingCentral — often create new HubSpot contacts when a call is logged, using the phone number as the identifier. If that contact already exists in HubSpot under their email address but without a phone number on file, the integration may create a second record rather than update the existing one.
Billing and subscription tools like Chargebee or Stripe follow the same pattern. A customer record created in the billing system does not always map cleanly to an existing HubSpot contact, and the integration creates a new one rather than finding the match.
Every new integration you add to your HubSpot stack is a potential new duplicate source. The question to ask at setup is always: what happens when this integration tries to create a record that already exists?
7. Manual data entry without duplicate checks
In most HubSpot portals, any user with contact creation permissions can create a new record without being warned that a similar record already exists.
A sales rep creates a contact for a prospect they met at an event. That prospect already exists in HubSpot from a form submission two years ago, under a different email and a slightly different company name. HubSpot shows no warning. Two records now exist.
This pattern scales with team size and tenure. The longer a team uses HubSpot, the more existing records accumulate. The more records there are, the harder it becomes for any individual to know whether a contact already exists before creating a new one. New team members are especially likely to create duplicates because they have no institutional memory of what is already in the system.
8. Team growth without CRM governance
Duplicates accumulate faster when more people have access to create records and there are no enforced standards for how records should be entered.
A team of three with clear CRM ownership tends to keep things relatively clean. A team of thirty, where sales, marketing, customer success, and operations all have HubSpot access and different habits for how they enter data, will accumulate duplicates quickly. Not out of carelessness, but because there is no system to prevent it.
As one HubSpot admin put it: "The team was a lot smaller and didn't care about data formality. That's why it's got to a point where there's a lot of issues with our data, more so duplicates."
This is the background rate of duplication that operates regardless of any specific integration or import event. It is slow, it is invisible until it is not, and it never stops on its own.
How to stop duplicates from building back up after a cleanup
A bulk cleanup removes the backlog. It does not address the sources that created it.
The causes above — form submissions, enrichment tools, Salesforce sync, imports, manual entry — continue operating after a cleanup. Without an ongoing deduplication process running in the background, the count starts climbing again within weeks.
The most effective approach is automated deduplication that runs continuously: detecting new duplicates as records are created or updated, and merging them against your defined rules without requiring manual intervention. That is what keeps a cleaned portal clean.
Duplicates do not have a single cause. They have several, all running simultaneously, all adding to the count at different rates. The ones worth focusing on first are the high-volume, continuous sources — enrichment tools, Salesforce sync, form submissions — because those are the ones that will refill a cleaned portal fastest if they are not addressed.
FAQ
What is the most common cause of duplicate contacts in HubSpot?
Imports and form submissions using different email addresses are the most common cause in most portals. The same person submits forms over time using different emails — personal, work, role-based — and HubSpot creates a new record each time rather than updating the existing one.
Does HubSpot prevent duplicates from being created?
HubSpot checks for exact email matches when a new contact is created via form submission or API, and will update an existing record if the email matches exactly. It does not check for fuzzy matches (name similarity, phone number, company name) which is where most duplication occurs in practice.
Why do I have duplicate companies in HubSpot but not duplicate contacts?
Company records in HubSpot have no single unique identifier equivalent to a contact's email address, which makes automatic deduplication harder. Companies are often created by integrations and enrichment tools using company name or domain, and slight variations — "Acme Inc" vs "Acme" vs "Acme Corporation" — all create separate records.
How do I know how many duplicates I have?
HubSpot's Manage Duplicates view gives you a floor estimate based on near-exact matching. For a complete picture — including fuzzy matches, integration-created duplicates, and company records — a dedicated deduplication tool will give you a more accurate count across all object types before you commit to a merge.
Can I prevent duplicates from being created by enrichment tools like Apollo or Clay?
You can reduce them by ensuring your enrichment tool checks against a broader set of identifiers before creating records — not just email, but domain, phone number, and company association. The more reliable long-term approach is running automated deduplication in the background to catch and merge new records as they are created, regardless of source.
Will cleaning up duplicates fix my HubSpot reports?
Yes. Duplicate records distort reporting because the same contact or company appears multiple times in lists, segments, and pipeline views. Merging duplicates consolidates the data onto a single record, which makes contact counts, company associations, and deal attribution accurate again.
