diff --git a/web/src/pages/OnboardingPage.tsx b/web/src/pages/OnboardingPage.tsx
index 4d6f1c3..106ab60 100644
--- a/web/src/pages/OnboardingPage.tsx
+++ b/web/src/pages/OnboardingPage.tsx
@@ -16,6 +16,7 @@ type Step = 1 | 2 | 3 | 4 | 5 | 6;
 
 type IncomeType = "regular" | "irregular";
 type BudgetConservatism = "tight" | "moderate" | "relaxed" | "custom";
+type FixedAmountMode = "fixed" | "estimated";
 
 type VariableCat = {
   id: string;
@@ -37,6 +38,7 @@ type FixedItem = {
   id: string;
   name: string;
   amountCents: number; // absolute amount
+  amountMode: FixedAmountMode;
   priority: number;
   dueOn: string; // yyyy-mm-dd
   frequency?: "one-time" | "weekly" | "biweekly" | "monthly";
@@ -139,6 +141,7 @@ export default function OnboardingPage() {
         setFixeds(
           s.fixeds.map((f: FixedItem) => ({
             ...f,
+            amountMode: f.amountMode === "estimated" ? "estimated" : "fixed",
             schedule: f.schedule ?? defaultSchedule(),
             autoPayEnabled: !!f.autoPayEnabled,
           }))
@@ -317,6 +320,7 @@ export default function OnboardingPage() {
         id: crypto.randomUUID(),
         name: "",
         amountCents: 0,
+        amountMode: "fixed",
         priority: list.length + 1,
         dueOn: getTodayInTimezone(userTimezone),
         frequency: "monthly",
@@ -405,6 +409,8 @@ export default function OnboardingPage() {
         const name = f.name.trim();
         if (!name) continue; // skip empties just in case
         try {
+          const amountMode = f.amountMode ?? "fixed";
+          const planAmountCents = Math.max(0, f.amountCents || 0);
           const schedule = f.autoPayEnabled
             ? {
                 frequency: "monthly" as const,
@@ -420,8 +426,10 @@ export default function OnboardingPage() {
           
           const created = await fixedPlansApi.create({
             name,
-            totalCents: f.amountCents,
+            totalCents: planAmountCents,
             fundedCents: 0,
+            amountMode,
+            estimatedCents: amountMode === "estimated" ? planAmountCents : null,
             priority: i + 1,
             dueOn: dueOnISO,
             frequency: f.frequency,
@@ -520,7 +528,11 @@ export default function OnboardingPage() {
         dashboardSnapshot.fixedPlans.map((p, i) => ({
           id: p.id,
           name: p.name,
-          amountCents: p.totalCents,
+          amountCents:
+            (p as any).amountMode === "estimated"
+              ? Number((p as any).estimatedCents ?? p.totalCents)
+              : p.totalCents,
+          amountMode: (p as any).amountMode === "estimated" ? "estimated" : "fixed",
           priority: i + 1,
           dueOn: p.dueOn,
           autoPayEnabled: false,
@@ -969,8 +981,8 @@ export default function OnboardingPage() {
                 <h2 className="section-title text-xl">Fixed Expenses</h2>
                 <p className="muted text-sm">
                   {incomeType === "regular" 
-                    ? "Set amounts for recurring bills and expenses" 
-                    : "Set amounts for recurring bills and choose payment planning options"}
+                    ? "Set fixed or estimated amounts for recurring bills and expenses" 
+                    : "Set fixed or estimated amounts and choose payment planning options"}
                 </p>
               </div>
 
@@ -1007,6 +1019,18 @@ export default function OnboardingPage() {
                       </button>
                     </div>
                     <div className="fixed-expense-fields">
+                      <select
+                        className="fixed-expense-select"
+                        value={f.amountMode}
+                        onChange={(e) =>
+                          updateFixed(f.id, {
+                            amountMode: (e.target.value as FixedAmountMode) || "fixed",
+                          })
+                        }
+                      >
+                        <option value="fixed">Fixed</option>
+                        <option value="estimated">Estimated</option>
+                      </select>
                       <CurrencyInput
                         className="fixed-expense-input"
                         valueCents={f.amountCents}
@@ -1030,6 +1054,11 @@ export default function OnboardingPage() {
                         <option value="monthly">Monthly</option>
                       </select>
                     </div>
+                    {f.amountMode === "estimated" && (
+                      <div className="text-xs muted mt-2">
+                        Estimated bills can be true-upped later in Settings by applying the actual amount.
+                      </div>
+                    )}
 
                     <label className="fixed-expense-checkbox">
                       <input
@@ -1183,6 +1212,11 @@ export default function OnboardingPage() {
                             <span className="review-item-meta">
                               Due {formatDateInTimezone(f.dueOn, userTimezone)}
                             </span>
+                            {f.amountMode === "estimated" && (
+                              <span className="review-item-badge">
+                                Estimated bill
+                              </span>
+                            )}
                             {f.autoPayEnabled && (
                               <span className="review-item-badge">
                                 {incomeType === "irregular" ? "Payment plan" : "Auto-fund"}