diff --git a/DECISIONS.md b/DECISIONS.md
index 3a3dc58..00b2efa 100644
--- a/DECISIONS.md
+++ b/DECISIONS.md
@@ -504,3 +504,9 @@ Implementation decisions not spelled out in `memory-bank/implementation-plan.md`
 - **Contracts carry an optional `scriptedId`** (sim `Contract` and API `contractSchema`) so the client can style scripted contracts and look up their flavor message.
 - **`SimContent` includes `scriptedTutorialContracts`;** the content bundle already provides it.
 - **Temporary:** the server passes `runsCompleted: 0` until Step 10A.7 adds the counter, so every server-generated board is a first-run board for now.
+
+## Step 10A.4
+
+- **The lender's cut is rounded down to whole credits:** repayment = `min(balance, floor(credits × share))`, or 0 when the balance is 0 or the credits after pilot pay are not positive. Credits are whole numbers everywhere, and rounding down favours the player by under one credit.
+- **`Resolution.credits` is now the net amount** (after pilot pay and repayment); `loanRepayment` is reported separately for the server to apply and the summary to show.
+- **Temporary:** the server resolves with `loanBalance: 0` until the balance column exists (Steps 10A.6 and 10A.9).
diff --git a/apps/server/src/game/resolve.ts b/apps/server/src/game/resolve.ts
index 3b03ded..067e4a0 100644
--- a/apps/server/src/game/resolve.ts
+++ b/apps/server/src/game/resolve.ts
@@ -43,7 +43,14 @@ export async function resolveArrivedDispatches(
     if (!pilot) throw new Error(`Dispatch ${dispatch.id} has no pilot`);
 
     const result = resolveDispatch(
-      { record: dispatch.record, pilotIsAvatar: pilot.isAvatar, discoveredIds, now },
+      // The loan balance is applied in Step 10A.9.
+      {
+        record: dispatch.record,
+        pilotIsAvatar: pilot.isAvatar,
+        discoveredIds,
+        loanBalance: 0,
+        now,
+      },
       content,
     );
     if (result.status !== "resolved") continue;
diff --git a/memory-bank/progress.md b/memory-bank/progress.md
index 78792b9..c8a1a15 100644
--- a/memory-bank/progress.md
+++ b/memory-bank/progress.md
@@ -109,7 +109,7 @@ Spec: `memory-bank/change-requests/CR-001-faster-start.md`. Decisions recorded a
 - [x] **Step 10A.1 — Content: new config and loaner ship.** `purchasable` on ShipModel; "Company Courier" (not purchasable, 6M km/h, 0.3 h overhead, 20 t); config: `tutorialLoanerShipModelId`, `tutorialRunsBeforeDeal` 4, `tutorialBoardSize` 3, `tutorialMassTonnes` 5/12/20, `handlingGameHoursPerTonne` 0.02, `loanRepaymentShare` 0.3, `dealLoanAmount` 5000, `startingCredits` 500. "Unmarked crates" scripted contract (run 3, ×2) and six onboarding goals (`src/data/onboarding.ts`). Step 2.5 test replaced per CR §6; Market lists purchasable models only and the server will not sell the loaner.
 - [x] **Step 10A.2 — Sim: handling time.** `travelTimeGameHours(ship, distance, massTonnes, config)` adds `mass × handlingGameHoursPerTonne`; dispatch records pass the contract mass (0 for repositions); client predictions pass contract mass. Step 3.5 hand-calculated test updated.
 - [x] **Step 10A.3 — Sim: tutorial board v2.** `generateTutorialBoard({ loanerLocationId, runsCompleted, periodIndex })`: light/medium/full Standard contracts at the tutorial share; a scripted contract for the upcoming run replaces the medium slot (`scriptedId` on the contract, at its pay multiplier). Loaner is `config.tutorialLoanerShipModelId`. Step 3.10 tests replaced. Server passes `runsCompleted: 0` until Step 10A.7.
-- [ ] Step 10A.4 — Sim: loan repayment
+- [x] **Step 10A.4 — Sim: loan repayment.** `splitLoanRepayment(credits, balance, share)` (`src/loan.ts`); `resolveDispatch` takes `loanBalance` and returns `loanRepayment` with net `credits`. Server passes a zero balance until Step 10A.9.
 - [ ] Step 10A.5 — Sim: onboarding goal evaluation
 - [ ] Step 10A.6 — Schema and database
 - [ ] Step 10A.7 — Server: tutorial flow v2
diff --git a/packages/sim/src/index.ts b/packages/sim/src/index.ts
index dc85bf2..f9e2b66 100644
--- a/packages/sim/src/index.ts
+++ b/packages/sim/src/index.ts
@@ -61,5 +61,8 @@ export { dispatchPosition, dispatchProgress } from "./flight";
 
 export { deliveryXp, pilotLevel, skillPointsAvailable } from "./xp";
 
+export { splitLoanRepayment } from "./loan";
+export type { LoanSplit } from "./loan";
+
 export { resolveDispatch } from "./resolution";
 export type { Resolution, ResolveInput, ResolveResult } from "./resolution";
diff --git a/packages/sim/src/loan.ts b/packages/sim/src/loan.ts
new file mode 100644
index 0000000..890cab7
--- /dev/null
+++ b/packages/sim/src/loan.ts
@@ -0,0 +1,17 @@
+export interface LoanSplit {
+  /** Credits that go to the lender. */
+  repayment: number;
+  /** Credits the player keeps. */
+  net: number;
+}
+
+/**
+ * Splits a payout between the lender and the player (decision 0.5.32): the
+ * lender takes `min(balance, credits × share)`, rounded down to whole credits,
+ * and nothing when there is no balance or no positive payout.
+ */
+export function splitLoanRepayment(credits: number, balance: number, share: number): LoanSplit {
+  if (credits <= 0 || balance <= 0) return { repayment: 0, net: credits };
+  const repayment = Math.min(balance, Math.floor(credits * share));
+  return { repayment, net: credits - repayment };
+}
diff --git a/packages/sim/src/resolution.ts b/packages/sim/src/resolution.ts
index bf4c050..df46120 100644
--- a/packages/sim/src/resolution.ts
+++ b/packages/sim/src/resolution.ts
@@ -1,11 +1,17 @@
 import type { SimContent } from "./board";
 import type { RealTime } from "./clock";
 import type { DispatchRecord } from "./dispatch";
+import { splitLoanRepayment } from "./loan";
 import { deliveryXp } from "./xp";
 
 export interface Resolution {
-  /** Credits to add: payout minus pilot pay. Fuel was already charged at departure. */
+  /**
+   * Credits to add: payout minus pilot pay, minus the loan repayment.
+   * Fuel was already charged at departure.
+   */
   credits: number;
+  /** Credits that went to the lender out of this payout (decision 0.5.32). */
+  loanRepayment: number;
   pilotXp: number;
   /** Where the ship (or tutorial loaner) is now. */
   shipLocationId: string;
@@ -21,12 +27,14 @@ export interface ResolveInput {
   /** The avatar is exempt from pilot pay (decision 0.5.12). */
   pilotIsAvatar: boolean;
   discoveredIds: ReadonlySet<string>;
+  /** The company's loan balance before this resolution. */
+  loanBalance: number;
   now: RealTime;
 }
 
 /** Resolves a dispatch once it has arrived. Same inputs always give the same result. */
 export function resolveDispatch(input: ResolveInput, content: SimContent): ResolveResult {
-  const { record, pilotIsAvatar, discoveredIds, now } = input;
+  const { record, pilotIsAvatar, discoveredIds, loanBalance, now } = input;
   if (now < record.arrivalAt) return { status: "in-flight" };
 
   const { contract } = record;
@@ -35,17 +43,29 @@ export function resolveDispatch(input: ResolveInput, content: SimContent): Resol
     // Repositions earn nothing and only fly to bays, which are already discovered.
     return {
       status: "resolved",
-      resolution: { ...base, credits: 0, pilotXp: 0, discoversDestination: false },
+      resolution: {
+        ...base,
+        credits: 0,
+        loanRepayment: 0,
+        pilotXp: 0,
+        discoversDestination: false,
+      },
     };
   }
 
   const pilotPay = record.tutorial || pilotIsAvatar ? 0 : content.config.pilotPayPerDelivery;
+  // Tutorial contracts already store exactly the tutorial share as their payout.
+  const { repayment, net } = splitLoanRepayment(
+    contract.payout - pilotPay,
+    loanBalance,
+    content.config.loanRepaymentShare,
+  );
   return {
     status: "resolved",
     resolution: {
       ...base,
-      // Tutorial contracts already store exactly the tutorial share as their payout.
-      credits: contract.payout - pilotPay,
+      credits: net,
+      loanRepayment: repayment,
       pilotXp: deliveryXp(record.distanceMillionKm, contract.tier, content.config),
       discoversDestination: !discoveredIds.has(record.destinationId),
     },
diff --git a/packages/sim/test/loan.test.ts b/packages/sim/test/loan.test.ts
new file mode 100644
index 0000000..5e68004
--- /dev/null
+++ b/packages/sim/test/loan.test.ts
@@ -0,0 +1,88 @@
+import { content } from "@deadhead/content";
+import { describe, expect, it } from "vitest";
+import {
+  createDispatchRecord,
+  resolveDispatch,
+  splitLoanRepayment,
+  type Contract,
+} from "../src/index";
+
+describe("loan repayment split", () => {
+  it("takes min(balance, credits × share), rounded down to whole credits", () => {
+    expect(splitLoanRepayment(1000, 5000, 0.3)).toEqual({ repayment: 300, net: 700 });
+    expect(splitLoanRepayment(1001, 5000, 0.3)).toEqual({ repayment: 300, net: 701 });
+    expect(splitLoanRepayment(1000, 120, 0.3)).toEqual({ repayment: 120, net: 880 });
+  });
+
+  it("takes nothing when there is no balance, or no positive payout", () => {
+    expect(splitLoanRepayment(1000, 0, 0.3)).toEqual({ repayment: 0, net: 1000 });
+    expect(splitLoanRepayment(0, 5000, 0.3)).toEqual({ repayment: 0, net: 0 });
+    expect(splitLoanRepayment(-60, 5000, 0.3)).toEqual({ repayment: 0, net: -60 });
+  });
+
+  it("always splits the whole amount and never repays more than the balance", () => {
+    for (const credits of [-500, -1, 0, 1, 7, 99, 1000, 123_457]) {
+      for (const balance of [0, 1, 50, 299, 5000, 1_000_000]) {
+        for (const share of [0, 0.1, 0.3, 1]) {
+          const { repayment, net } = splitLoanRepayment(credits, balance, share);
+          expect(net + repayment).toBe(credits);
+          expect(repayment).toBeLessThanOrEqual(balance);
+          expect(repayment).toBeGreaterThanOrEqual(0);
+          expect(repayment).toBe(
+            credits > 0 && balance > 0 ? Math.min(balance, Math.floor(credits * share)) : 0,
+          );
+        }
+      }
+    }
+  });
+});
+
+describe("resolution with a loan", () => {
+  const now = Date.parse("2100-01-01T00:30:00Z");
+  const contract: Contract = {
+    id: "c1",
+    originId: "earth",
+    destinationId: "moon",
+    cargoTypeId: "standard",
+    tier: 0,
+    massTonnes: 10,
+    payout: 2000,
+    requiredSkill: null,
+    requiredLongHaulLevel: 0,
+    offeredAt: now,
+    expiresAt: now + 3_600_000,
+    firstContact: false,
+  };
+  const record = createDispatchRecord(
+    {
+      id: "d1",
+      ship: { id: "s1", modelId: "courier", locationId: "earth", inFlight: false },
+      pilot: { id: "p1", isAvatar: false, assignedShipId: "s1", inFlight: false, skills: {} },
+      contract,
+      tutorial: false,
+      now,
+      worldSeed: 7,
+    },
+    content,
+  );
+
+  it("returns the repayment alongside the credits to add, after pilot pay", () => {
+    const result = resolveDispatch(
+      {
+        record,
+        pilotIsAvatar: false,
+        discoveredIds: new Set(["earth", "moon"]),
+        loanBalance: 5000,
+        now: record.arrivalAt,
+      },
+      content,
+    );
+    if (result.status !== "resolved") throw new Error("expected a resolution");
+    const afterPay = 2000 - content.config.pilotPayPerDelivery;
+    const repayment = Math.floor(afterPay * content.config.loanRepaymentShare);
+    expect(result.resolution).toMatchObject({
+      loanRepayment: repayment,
+      credits: afterPay - repayment,
+    });
+  });
+});
diff --git a/packages/sim/test/resolution.test.ts b/packages/sim/test/resolution.test.ts
index 5918731..4ddc25a 100644
--- a/packages/sim/test/resolution.test.ts
+++ b/packages/sim/test/resolution.test.ts
@@ -41,6 +41,7 @@ const arrived: ResolveInput = {
   record,
   pilotIsAvatar: false,
   discoveredIds: new Set(["earth", "moon"]),
+  loanBalance: 0,
   now: record.arrivalAt,
 };
 
@@ -106,6 +107,7 @@ describe("dispatch resolution", () => {
     );
     expect(resolve({ ...arrived, record: reposition, now: reposition.arrivalAt })).toEqual({
       credits: 0,
+      loanRepayment: 0,
       pilotXp: 0,
       shipLocationId: "moon",
       discoversDestination: false,