Fundraising · Auctions
Silent auction net proceeds.
Starting bid, reserve and what your group nets on an item.
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Silent Auction Net Proceeds Calculator: how it works
Starting bid = fair market value x the share you choose (50% is a common rule of thumb, not a published standard). Reserve = your cost / (1 - fee rate), the lowest bid that covers cost after fees. Net proceeds = winning bid - fee - your cost. The part of a bid above fair market value is what the IRS treats as potentially deductible for a US bidder.
Worked example. A donated item worth $200.00 with a 50% starting share opens at $100.00. A winning bid of $160.00 with a 3% fee ($4.80) nets $155.20, which is 80% of value. For an item your group paid $120.00 for, the reserve is $123.71; a $90.00 bid would net -$32.70, below that reserve.
Receipts differ by country. Under IRS Publication 526, a bidder at a charity benefit event can deduct only the amount above the fair market value of what they receive. Other countries have their own rules, so check your tax authority before issuing receipts. Fair market value must be a real, defensible figure.
Frequently asked questions
How do I set a starting bid for a silent auction?
Many organizers open at a share of fair market value. 50% of $200.00 is $100.00; that share is a rule of thumb you set, not a published standard.
What is a reserve price?
The lowest bid you will accept. A reserve of cost divided by 1 minus the fee rate covers what you paid and the fees. Here, $123.71 for a $120.00 item.
How much of the winning bid is a donation?
In the US, per IRS Publication 526, only the amount above the fair market value of what the bidder receives can be deductible. A bid at or below value has no deductible part.
Do fees come off the net?
Yes. Enter the percentage your payment processor charges and it is subtracted from the winning bid.
Sources
Checked
- Publication 526 (2025), Charitable Contributions (Internal Revenue Service), opened 8 October 2026.
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Not professional advice
Arithmetic only. Charitable receipting and tax rules vary by jurisdiction; check your tax authority. Not tax or legal advice.