Only projects working with fiscal sponsors can offer tax deductible pledges. Pledges placed to campaigns not working with a fiscal sponsor are not tax deductible.
Campaigns will typically indicate whenever they're working with a fiscal sponsor.
If you have any questions about a specific project that you want to pledge towards, we recommend messaging the creator directly and asking them about their ability to offer a tax deductible pledge.
Regarding any matters around taxes, we always recommend consulting a tax and/or financial professional.