If i take in 50k of income and donate 40k to a 501(c)(3) non-profit, how much money will have to pay taxes on?
I am a sole proprietorship.
At least on 25K. Here's the actual IRS publication, it's fairly complex and the limits depend on the types of organization you're donating to, and the types of property you're donating. Some donations may be limited to the maximum of 20% of your AGI.
Bottom line - the maximum you can deduct in almost all circumstances would be 50% of the AGI (very few exceptions allow deducting up to 100% of your AGI).
Worth mentioning that whatever you cannot deduct this year - you can roll over to the next year.