Mosaic Research · St. Louis County Tax Sale
Investor Strategy Guide · Preview

St. Louis County's Tax Auction: winning bidders are losing thousands.

Sealed bids. One number, submitted blind — often double what it needed to be, sometimes triple.

2026 sale begins Monday, August 24 · sealed bids due 5pm Wednesday, August 26

You will not see another bidder's number before you commit to yours. Nobody will. St. Louis County's delinquent-tax sale is sealed: every bid is locked in before any is opened. Whatever price discipline you bring to that envelope, you bring alone.

Between 2020 and 2024, bidding alone got more expensive. The median winner on a contested parcel went from paying 33% over the next-highest bid to 51% over it.

Median margin over runner-up
$3,009 → $7,904
Sale years 2020 → 2024
What the winner paid above the next-highest bid, at the median of contested parcels. An increase of 163%.
Won at 2× the runner-up or more
10.2% → 28.5%
Share of contested parcels. The 3×-or-more share rose from 1.9% to 10.5% over the same window.

Rising premiums usually mean more competition. There was less.

Bids per contested parcel
3.44 → 2.86
Average, 2020 to 2024. The most-bid parcel of the year went from 13 bids down to 8.

Fewer rivals, higher premiums, and no way to see either

Those two numbers are supposed to move together. That they moved apart rules out the ordinary explanation, because in a sealed sale there is nothing to react to. No rival bid these prices up. There was no rival to see.

Which leaves the question of what any of these bids were measured against. Here the public record fails, and it fails every bidder the same way.

Bidders appear in the public record as a registration number, and no number survives more than two sales. Across five sales there are 518 distinct bidder numbers: 459 appear in exactly one year, 59 in exactly two, and none appears in three or more. In a five-year window with known repeat participants, the record carries no identity across time. Read it straight and every sale looks like a fresh set of strangers.

It isn't. Working from the county's own bidder-registration rosters — some obtained under the Missouri Sunshine Law, some supplied by a St. Louis County real-estate attorney — we matched names back to numbers, one year at a time. The continuity comes straight back: the most active buyer holds 271 parcels across four sales, under a rotating set of single-purpose LLCs.

Those rosters name every winner in 2021, 2022 and 2024. For 2020 they name 56%, because the county's unsuccessful-bidder file for that year carries no bidder numbers to join on — so every 2020 figure here is a floor, not a total. For 2023 no roster has been released; our records request for it is paid and outstanding.

We don't name the buyers here. The guide does, with each one's entry year, exit year, win rate, and margin trend.

So the premium is not set by competition, and not against a field anyone could identify. It is set against a blank — and nothing in the public file fills it in.

What the premium buys

Figure 1
What the premiums add up to, year by year.
Paid 2×–3× the runner-up Paid 3× or more
$0 $600K $1.2M $1.8M $2.4M $282K $553K $801K $2.14M $2.20M 2020 2021 2022 2023 2024
Total dollars paid above the runner-up bid, by year, counting only the parcels won at double the next-highest bid or more. The lower band is parcels won at 3× or more; the upper band is 2× to 3×. Hover any year for the parcel counts behind it.

Inside the Investor Strategy Guide

$249. Delivered on purchase — ahead of the August 26 bid deadline. If our outstanding records request releases the 2023 roster, buyers receive the addendum at no charge.
See what you receive, and buy →To purchase, write research@mosaicsyndicate.com.

In 2020, the parcels won at double the runner-up or more paid $282,000 above what the sale required. In 2024, they paid $2.20 million — nearly eight times as much, while the contested field thinned from 3.44 bids per parcel to 2.86. Under RSMo 140.340, not one dollar of it earns a cent. That is what bidding without the record costs, and it is the part we built this to stop.

Methodology: compiled from St. Louis County delinquent-tax sale bid records covering every bid placed, not only winning bids — 5,116 bids across 2,141 parcels, sale years 2020–2024. Margin figures describe the gap between the winning bid and the next-highest bid on the same parcel; they describe what bidders paid relative to one another and make no claim about any parcel's value. Contested parcels are those drawing two or more bids. The 2026 sale is sealed-bid under the county's published instructions; that the 2020–2024 sales were also single-sealed-bid is inferred from the bid record rather than from a county statement of format — across all 5,116 bids, no bidder placed a second bid on the same parcel in the same year. Figures are reproducible from the county bid record. This document is market research. It is not legal, tax, or investment advice, it recommends no bid on any parcel, and it forecasts no future sale. We strive to exceed your expectations with honesty and transparency.