In general, gifts to charity are deductible if you have a receipt or statement from the charity (for example, a letter thanking you for donating certain food or supplies). The charity must be registered with the IRS as an exempt organization. The letter does not have to place a dollar value on the donation -- you will do that with your own receipts -- but you need some kind of written acknowledgment.
However, if you are a principal -- you run the ministry -- you can run into audit trouble for claiming tax deductions for donations that benefit you personally. Questions could arise about whether the donation really supported the ministry, for example. As another example, if you are a chaplain who travels around several hospitals, your lunch while driving around town is not a tax deductible business expense, and you can't turn it into a deduction by claiming it as a charitable donation.
When you are a principal of the charity, it is best to have someone else write that letter. For example, when I was a church treasurer, I sometimes provided supplies for the church as a donation, but I had someone else sign the acknowledgment letter (such as the pastor or the head trustee) so there would be a paper trail showing that someone else in the organization agreed that the donation was real, and was to the church's benefit and not my own benefit.
If you are self-employed as an independent contractor, some expenses may be deductible as unreimbursed business expenses, even if they are not charitable donations. They must be ordinary and necessary expenses of your business, and the fact that your business is a ministry does not really change how those rules are applied. If you are an employee of the organization and paid as a minister (exempt from certain withholding but required to pay self-employment tax), then unreimbursed business expenses are not deductible from your box 1 wages, but may be deductible from your income subject to self-employment tax, through application of the Deason rule (this requires you to do your own calculations and make a manual entry in Turbotax). An employee who performs ministerial duties is also eligible to have part of their salary designated as a non-taxable housing allowance, and there are special rules that must be followed, and a housing allowance can't be retroactive (meaning you could set one up tomorrow to cover your expenses for the rest of 2026, but you can't take advantage of it for 2025).
Those are a lot of general principles and rules. To be more specific, I need to know more about your situation.
