Neuruh - Evidence-first underwriting - Engine E12

Tax Sale / Auction Bid Engine

Tax deed sales and tax lien certificate auctions. Auction and redemption rules for the jurisdiction, max bid, redemption risk, title risk, post-auction plan, and holding cost. Ends in the shared E13 Risk / Kill-Switch.

Versionv1.0
Date2026-11-04
StatusEngine 12 of 12 - Active
LineageCodex V2 App. B, E12 + Residential v1.1 gates + E1 land engine pattern
Not an appraisal. Not legal or tax advice. Not a title opinion. Public-data underwriting only. Tax sale rules change by state and by county, and a wrong redemption period or a missed senior lien can erase the deal. Verify the auction rules, the redemption period, and title with the county treasurer, the county clerk, and a licensed title company or attorney before bidding. No offer without Jeramie. Offer authorized is false on every run. A bid at auction is a binding purchase, not an offer to negotiate.

00Try it in 60 seconds

Three steps. No sign-up, no data leaves your browser.

  1. Step 1: Load Sample A with the button below.
  2. Step 2: Change Resale Value in section 03.
  3. Step 3: Watch Max Bid, Net if Kept, and Expected Value move in the sticky results panel and in section 10.
Max bidN/A
Headroom over minimum bidN/A
Expected valueN/A
RecommendationHOLD
Completeness 0 percent

01Parcel and auction identity

Address / parcel gate. Confirm the parcel from at least 2 public sources before any number is used. The auction listing itself is one source, not two.

02Auction and redemption rules for the jurisdiction

Jurisdiction rules gate. Tax sale rules are set by state statute and run by the county. A rule copied from another state is not a rule for this parcel. Every line needs a county or statute source, or it is N/A.

03Value, repairs, minimum bid

Value gate. Resale value is the after-repair value of the property, from comps, not from the auction listing. Repairs are a scope, not a guess. The minimum bid is the auction opening bid from the listing.

04Max bid

Deterministic math. Max bid is the highest hammer bid that still leaves the stated profit after repairs, holding, title, and senior liens. Senior liens are paid on top of the bid, so they come out of the max bid dollar for dollar.

Max Bid = Resale Value - Repairs - Holding Total - Title Costs Total - Desired Profit - Senior Liens
Headroom = Max Bid - Minimum Bid
Desired Profit = Resale Value x Profit Percent / 100
Max bid is the hammer bid before any buyer premium. Buyer premium is shown separately in section 05.
Resale valueN/A
Less repairsN/A
Less holding total (section 07)N/A
Less title costs total (section 06)N/A
Less desired profit (0%)N/A
Less senior liensN/A
Max bidN/A
Minimum bidN/A
Headroom over minimum bidN/A
Planned bid used in section 05N/A
Figure 1. Max bid waterfall, Sample A numbers. Resale value $120,000 less repairs $15,000, holding $3,600, title $1,000, profit $24,000, and senior liens $0 gives a max bid of $76,400. The waterfall is illustrative; the live numbers are in the table above.
MAX BID WATERFALL, SAMPLE A (dollars) Resale 120,000 Repairs 15,000 Holding 3,600 Title 1,000 Profit 24,000 Max bid 76,400 Bar length is resale value scaled to 480 px. Senior liens 0 in Sample A.

05Redemption risk

Redemption math. If the owner redeems, the bidder gets the bid back plus interest, and keeps none of the property upside. The model is conservative: redemption payoff is bid plus interest only, and costs paid at purchase are not reimbursed.

Interest Earned = Planned Bid x Redemption Rate / 100 x Redemption Months / 12
Redemption Payoff = Planned Bid + Interest Earned
Net if Redeemed = Interest Earned - (Monthly Holding x Redemption Months) - Costs at Purchase - Buyer Premium
Net if Kept = Resale Value - Repairs - Holding Total - Title Costs Total - Planned Bid - Buyer Premium
Expected Value = (1 - Redemption Probability) x Net if Kept + Redemption Probability x Net if Redeemed
Redemption interest earnedN/A
Redemption payoff (bid plus interest)N/A
Buyer premium on planned bidN/A
Deposit due at auctionN/A
Net if redeemedN/A
Net if keptN/A
Expected valueN/A
Enter a redemption probability to compute expected value. A probability with no basis in the notes is a guess: write the basis or leave it N/A.
Figure 2. Redemption timeline, Sample A. Auction at month 0, redemption expires at month 6, quiet title and marketing run months 6 to 9, exit at month 9. If the owner redeems in months 0 to 6, the bidder is repaid bid plus interest and the deal ends. The timeline is illustrative; the live months are in section 07.
Month 0Auction Month 6Redemption ends Month 6-9Title + market Month 9Exit REDEMPTION WINDOW: MONTHS 0 TO 6, INTEREST 12% PER YEAR

06Title risk

Title gate. A tax deed does not guarantee insurable title. Quiet title is a real cost and a real timeline. If title is uninsurable and there is no quiet-title budget, the run is a PASS.

Title costs totalN/A
Costs at purchase (sunk if redeemed)N/A
Quiet title cost (spent only if not redeemed)N/A

07Holding cost

Holding math. Holding months are the redemption months plus the post-redemption months (quiet title, marketing, and exit). If the redemption period is unknown, holding months and holding total are N/A, and max bid is N/A.

Monthly Holding = Taxes + Insurance + Maintenance + Interest + Other
Holding Months = Redemption Months + Post-Redemption Months
Holding Total = Monthly Holding x Holding Months
Monthly holdingN/A
Holding months (redemption + post-redemption)N/A
Holding totalN/A
Holding during redemption onlyN/A

08Post-auction plan

A bid with no post-auction plan is a speculation, not an underwrite. State the plan, the timeline, and who does the work. If the property is occupied, state the possession plan or mark it missing.

09Gates - fail closed

Any gate at fail or hold shows HOLD. Do not round a hold up to a pass. A kill in section 13 overrides a pass here: a PASS is still a PASS.

Gate statusHOLD - gates not verified
Gates passedNone
Gates failed or heldAll
Missing for a GO: parcel, county, auction date, auction type, resale value, minimum bid, redemption period, title status.

10Results

All outputs in one place. A number is N/A when an input it depends on is N/A. N/A is a correct answer, not a gap to fill with a guess.

0 percent complete.
Max bidN/A
Headroom over minimum bidN/A
Planned bidN/A
Holding totalN/A
Title costs totalN/A
Net if keptN/A
Net if redeemedN/A
Expected valueN/A
RecommendationHOLD

11Receipt

Generated from the inputs above. Matches the tax-sale-receipt v1.0 schema fields. Offer authorized is always false in this tool. A bid at auction is a binding purchase, so this receipt is evidence, not permission to bid.

{}

12One-page summary - print this

The deal on one page. Print this section for the file copy. It updates live from the inputs above.

Parcel IDN/A
CountyN/A
Auction dateN/A
Auction typeN/A
Redemption periodN/A
Title statusN/A
Max bidN/A
HeadroomN/A
Net if keptN/A
Expected valueN/A
Confidence0.50
GatesHOLD
RecommendationHOLD

13E13 Risk / Kill-Switch (shared)

Every engine ends here. List the kill conditions that fired, the risk flags, and the explicit PASS recommendation if any fired. A PASS is a successful run, not a failed one.

Kill-switch activeNo
Kill reasonsNone
RecommendationHOLD
Flags raised in this runNone

E12 contract kill conditions: (1) redemption period unknown, (2) title uninsurable with no quiet-title budget. The other kills in the list above are engine-level kills: max bid below the minimum bid means no profitable bid exists, unverified auction rules mean the redemption math has no basis, and an unpriced senior lien means the max bid is built on an unknown cost.

14How it works / What this is not

Read this before relying on any number on this page.

How it works: confirm the parcel from at least 2 public sources, verify the auction and redemption rules for the county from the county or statute source, enter resale value from comps, repairs, title costs, and monthly holding costs. The tool computes holding total, title total, desired profit, max bid, headroom, redemption payoff, net if redeemed, net if kept, and expected value from the exact formulas in sections 04, 05, and 07. Gates fail closed. A kill means PASS. The receipt records what was entered, what passed, and what was N/A. A share link encodes the whole deal in the URL so someone else can open the same numbers.

What this is not: not an appraisal, not a survey, not legal or tax advice, and not a title opinion. It does not check the auction listing for you, does not confirm the redemption period, does not run a title search, and does not guarantee the property is vacant, the title is insurable, or the owner will not redeem. It does not invent rules, prices, comps, or source claims. If a field cannot be verified, it stays N/A. No bid is placed without Jeramie.

Honest gaps and limits. This engine does not pull live county data: every rule, bid, and lien must be typed in from a source you checked. It does not model bidding competition, so a max bid is a ceiling, not a prediction of the winning bid. It does not model senior lien priority beyond the dollar amount you enter; lien priority is a title question. It does not model eviction cost or timeline beyond the possession plan note. Redemption probability is your estimate, not a measured rate; expected value moves with it, so state the basis. Layout was not eyeballed in a real browser. Sample deals are synthetic and labeled as such; they use example county names and example source references, not real records.

Related modules. Resale value for a house deal comes from the Residential Underwriting Engine. Land value, zoning, and split math come from E1 Land and Zoning Unlock. Title defects that need a cure-cost workup go to E8 Distressed Title when it is built. The hub is the Real Estate Agent hub.