A taxpayer can deduct out-of-pocket expenses related to volunteer work for “qualifying organizations”. Those deductions are reported on Schedule A – Itemized Deductions. I assume when you say “Little Sister” you mean the recipient of your volunteering, not actually your little sister? Those expenses would be deductible. You should speak to your Big Brother/Big Sister supervisor. If they reimburse you, then it would not be deductible. HOWEVER, this would apply to your 2017 taxes, the rules are different for next years taxes. As Thomas mentioned, you’ll need to talk to your tax advisor for more information.