I paid my property taxes with a credit card that charged a convenience fee. Can I deduct the convenience fee?

If you itemize deductions, likely the convenience fee is tax deductible. The IRS hasn’t said whether this specific convenience fee is deductible as part of your real estate taxes (which has no income threshold) or as a miscellaneous itemized deduction (which has a 2%-of-adjusted-gross income threshold), but prior guidance (IR-2009-37) on a similar topic may be helpful: The IRS ruled that the convenience fee paid when charging federal income taxes was deductible, but only as a miscellaneous itemized deduction.