When you import a spreadsheet, Taguchi checks each row to decide whether to update an existing subscriber or create a new profile. It also adds or updates that subscriber's membership in the list you are importing into.

Understanding this matching process helps you avoid creating a second profile for someone who is already in your database, or changing information you intended to keep. Your choice of fields in Map columns determines which details Taguchi uses.

Which subscriber is matched?

An identifier is a value used to recognise the subscriber, such as an email address or customer number.

• Map at least one available identifier: External ID, Email or Phone.
• Use Subscriber ID only if it is enabled for your account.
• Include any additional values required by your organisation's import rules. Those rules can also restrict which identifiers are available.

Taguchi looks for matches within your organisation. It checks the identifiers in this order:

Uploaded identity	Matching behaviour
Subscriber ID	An exact existing Subscriber ID is checked first.
External ID	An exact External ID is checked next if the row has not matched by Subscriber ID.
No uploaded External ID	The importer can match by email and phone, then email, then phone under the conditions below.

Take care when including External ID:

• If Taguchi cannot find the supplied External ID, it will not then use the row's email or phone to find an existing subscriber.
• The row can create a separate profile even if the email address already exists.
• Use the same External IDs consistently across your imports.

For example:

1. Alex already has a profile with Email `alex@example.com` and no External ID.
2. Your file contains Email `alex@example.comand External IDcustomer-001`.
3. If that External ID does not exist, the import can create a separate subscriber. It does not find Alex by email and add the new External ID to that profile.

When the uploaded External ID is blank or omitted:

• A matching email-and-phone combination is checked before email alone.
• Email matching ignores letter case.
• Phone matching is used only when either the uploaded row or the existing subscriber has no email.
• Where several profiles qualify, the importer prefers a profile without a global unsubscribe, then the lowest Subscriber ID.

If no existing profile matches, the row needs a usable External ID, Email or Phone to create a subscriber. A Subscriber ID that does not exist is not enough to create a new profile.

Check the actual values as well as the column mappings. For example, a blank phone number or an email address without @ cannot identify a subscriber. An address passing this check does not confirm that the mailbox exists or can receive messages.

What happens if the same subscriber appears more than once?

Updating a person who is already in Taguchi is a normal use of imports. Your spreadsheet can also contain more than one row for the same subscriber.

If two rows contain Alex's email address but different first names:

• Do not rely on the last row to determine the final name.
• Repeated rows may be reported as Duplicate or match a profile already processed, because large files are processed in smaller groups.

Before importing, combine the information you want to keep into one row for each subscriber and remove conflicting copies.

Omitted fields and blank cells

Leaving a field out of your spreadsheet is different from including an empty cell in a column you map.

For example, if you are updating phone numbers, you can omit the First name column to keep existing names. If you include First name, map it and leave Alex's cell empty, that empty value can clear Alex's existing first name.

Choosing Ignore column also leaves the existing field unchanged. Use the table below to check how a mapped blank cell is handled.

Field or value	Effect on an existing subscriber
Ignored or omitted field	Existing value is preserved.
Blank Email, Phone or External ID	Existing value is preserved.
Blank mapped text profile field, such as First name	Can clear the existing text.
Blank mapped subscriber custom field	Can clear the existing value.
Blank date of birth or a value Taguchi cannot read as a date	Existing date of birth is preserved.
False/blank unsubscribe or invalid flag	Does not clear an existing status.
Blank mapped Subscription option	Clears the existing list-option text.
Blank mapped Partition external ID	Clears existing partition assignments.

Use a small demonstration import to check the fields you intend to change before processing a large file.

List membership and unsubscribe status

The import adds or updates membership in the destination list. Updating a subscriber's profile does not reset an existing global unsubscribe or invalid status. False/blank unsubscribe flags do not resubscribe an existing subscriber.

A destination list's configured email/phone uniqueness rules can also affect which memberships remain subscribed. See unique subscription enforcement.

Partition membership

Mapping Partition external ID replaces existing partition assignments with the valid references supplied. It does not simply add to the current set. See mapping partition external ID before importing that field.

Related guides

• Upload subscriber data into a list
• Bulk Upload Errors
• Already unsubscribed or invalid subscribers

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