I've made purchases on personal credit cards for business purposes. Is that tax deductible?
Yes just keep the required supporting docs for the deduction ...
https://www.irs.gov/businesses/small-businesses-self-employed/what-kind-of-records-should-i-keep
https://turbotax.intuit.com/tax-tools/tax-tips/Small-Business-Taxes/Taking-Business-Tax-Deductions/I...