Do I need to pay taxes if I received a check more than $14000 If the donor doesn't declare the money as a gift?

[fanfare]

A gift is not taxed.

any gift tax reporting requirement is the donor's issue.

[tagteam]

"Do I need to pay taxes if I received a check more than $14000 If the donor doesn't declare the money as a gift?"

It is possible, per Section 6324(b), to have donee liability for any unpaid gift taxes owed and not paid by the donor.

See https://www.irs.gov/irm/part5/irm_05-005-007.html#d0e1463

[Hal_Al]

"Gift Tax" is somewhat of a misnomer.  Even though a gift tax return may be required, very few people ever actually pay federal gift tax. The purpose of the gift tax return is usually only to document a reduction in the allowable estate tax exemption.
See https://turbotax.intuit.com/tax-tools/tax-tips/Tax-Planning-and-Checklists/The-Gift-Tax-Made-Simple/...

If you know, for sure, the purpose and intent of the check is as a gift to you, you don't need to worry about it.