How online book auctions work: estimates, buyer’s premium and bidding
A practical guide to buying books at online auctions on Catawiki, Heritage, Invaluable and the-saleroom: what estimates mean, what you really pay and how to bid.
· 2 min read
Auctions are where many of the most interesting books change hands: signed copies, association copies, early printings and whole collections. Buying online is easy once you understand a few terms.
Platforms and auction houses
Some platforms run their own auctions (Catawiki, Heritage Auctions). Others, like Invaluable and the-saleroom, are marketplaces where hundreds of independent auction houses publish their catalogues and take bids online. The rules, fees and shipping depend on the house running the sale, so always read the terms of each auction.
Estimates
Most lots show an estimate, such as “£300–£500”. It’s the auction house’s view of what the lot will fetch, not a price. Books often sell below the low estimate when interest is thin and well above the high estimate when two determined bidders meet.
Many lots also have a confidential reserve: the minimum the seller will accept. If bidding doesn’t reach it, the lot goes unsold.
What you actually pay
The hammer price is the winning bid. On top of it you’ll usually pay:
- Buyer’s premium: a percentage of the hammer price charged by the auction house. It commonly falls somewhere between 20% and 30%, and some houses charge more.
- Tax on the premium, and sometimes on the hammer price, depending on the country.
- Online bidding fees on some platforms.
- Shipping and insurance, often arranged through a third party after the sale.
A £400 hammer can easily become well over £500 delivered. Work out your maximum total before you bid, then convert it back into a maximum hammer price.
Ways to bid
- Absentee or maximum bids: you leave your highest bid and the platform bids for you, one increment at a time, up to that limit. This is the calmest way to buy.
- Live online bidding: you bid in real time while the sale happens. Exciting, and easy to overspend.
- Timed auctions: common on Catawiki and in online-only sales; lots close at a set time, sometimes extended if bids arrive at the last minute.
Questions to ask before bidding
- Condition report. Ask for one; it’s free. Ask specifically about the dust jacket, foxing, previous repairs and whether pages are complete.
- Photos of the edition statement and copyright page if they aren’t shown.
- Provenance and authentication for signed lots: who has examined the signature, and is there a letter of authenticity?
Don’t miss the sale
Lots are often online for only a week or two before the sale, across many different houses. ShelfProud searches Catawiki, Heritage, Invaluable and the-saleroom alongside the marketplaces and tells you when a new lot matching your search is listed, with its estimate and sale date.