diff --git a/src/app/(main)/report/page.tsx b/src/app/(main)/report/page.tsx
index 0bd8e61b..06d4006d 100644
--- a/src/app/(main)/report/page.tsx
+++ b/src/app/(main)/report/page.tsx
@@ -57,6 +57,21 @@ interface ItemCodeWithName {
   name: string;
 }
 
+/** Months from the earliest ledger month through the current month. Value stays YYYY-MM-01. */
+function ledgerMonthOptions(isZh: boolean, earliest: string) {
+  const start = dayjs().startOf('month');
+  let end = dayjs(earliest).startOf('month');
+  if (!end.isValid() || end.isAfter(start)) end = start;
+  const count = start.diff(end, 'month') + 1;
+  return Array.from({ length: count }, (_, i) => {
+    const d = start.subtract(i, 'month');
+    return {
+      value: d.format(OUTPUT_DATE_FORMAT),
+      label: isZh ? `${d.year()}年${d.month() + 1}月` : d.format('MMMM YYYY'),
+    };
+  });
+}
+
 const FIELD_ERROR_SX = {
   '& .MuiOutlinedInput-root.Mui-error': {
     '& .MuiOutlinedInput-notchedOutline': {
@@ -97,6 +112,7 @@ export default function ReportPage() {
     session?.abilities?.includes(AUTH.ADMIN) ?? false;
 
   const [selectedReportId, setSelectedReportId] = useState<string>('');
+  const [ledgerEarliest, setLedgerEarliest] = useState<{ reportId: string; earliest: string } | null>(null);
   const [criteria, setCriteria] = useState<Record<string, string>>({});
   const criteriaRef = useRef<Record<string, string>>({});
   const pendingItemCodeInputRef = useRef<Record<string, string>>({});
@@ -269,6 +285,32 @@ export default function ReportPage() {
     }
   };
 
+  // Earliest stock_ledger month for the period-start list. Newest month is always the current month.
+  useEffect(() => {
+    const endpoint = currentReport?.fields.find(
+      (field) => field.type === 'month' && field.earliestMonthEndpoint,
+    )?.earliestMonthEndpoint;
+    if (!currentReport || !endpoint) return;
+    const reportId = currentReport.id;
+    let cancelled = false;
+    (async () => {
+      try {
+        const response = await clientAuthFetch(endpoint);
+        if (!response.ok) return;
+        const data = await response.json();
+        const earliest = typeof data?.earliest === 'string' ? data.earliest : '';
+        if (!cancelled && earliest) {
+          setLedgerEarliest({ reportId, earliest });
+        }
+      } catch (error) {
+        console.error('Failed to load ledger months', error);
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, [currentReport]);
+
   // Load initial options when report is selected
   useEffect(() => {
     if (currentReport) {
@@ -661,6 +703,50 @@ export default function ReportPage() {
                   field.name === 'status' &&
                   rep012MultiRound;
 
+                if (field.type === 'month') {
+                  const earliestForReport =
+                    ledgerEarliest?.reportId === currentReport.id ? ledgerEarliest.earliest : '';
+                  const monthOptions = earliestForReport
+                    ? ledgerMonthOptions(isZh, earliestForReport)
+                    : [];
+                  return (
+                    <Grid item {...gridSize} key={fieldKey}>
+                      <TextField
+                        select
+                        fullWidth
+                        required={field.required}
+                        error={Boolean(fieldErrors[field.name])}
+                        helperText={fieldErrors[field.name] || undefined}
+                        label={translatedLabel}
+                        value={currentValue}
+                        disabled={disabledByCheckedCheckbox || disabledRep012Status || !!field.disabled}
+                        onChange={(e) => handleFieldChange(field.name, e.target.value)}
+                        sx={{
+                          ...FIELD_ERROR_SX,
+                          ...(currentReport.id === 'rep-005' ? {
+                            '& .MuiOutlinedInput-root': {
+                              minHeight: '64px',
+                              fontSize: '1rem'
+                            },
+                            '& .MuiInputLabel-root': {
+                              fontSize: '1rem'
+                            }
+                          } : {}),
+                        }}
+                      >
+                        <MenuItem value="" disabled>
+                          {isZh ? '請選擇月份' : 'Select month'}
+                        </MenuItem>
+                        {monthOptions.map((opt) => (
+                          <MenuItem key={opt.value} value={opt.value}>
+                            {opt.label}
+                          </MenuItem>
+                        ))}
+                      </TextField>
+                    </Grid>
+                  );
+                }
+
                 if (field.type === 'date') {
                   const parsed = currentValue ? dayjs(currentValue) : null;
                   const dateError = fieldErrors[field.name];
diff --git a/src/config/reportConfig.ts b/src/config/reportConfig.ts
index b01954f4..483e61cf 100644
--- a/src/config/reportConfig.ts
+++ b/src/config/reportConfig.ts
@@ -1,5 +1,5 @@
 /** FP-MTMS Version Checklist | Functions Ref. No. 39 | v1.0.0 | 2026-08-03 */
-export type FieldType = 'date' | 'text' | 'select' | 'number' | 'checkbox';
+export type FieldType = 'date' | 'month' | 'text' | 'select' | 'number' | 'checkbox';
 
 import { NEXT_PUBLIC_API_URL } from "@/config/api";
 
@@ -29,6 +29,8 @@ export interface ReportField {
   multiline?: boolean;
   /** Rows for multiline text areas. Default 4. */
   minRows?: number;
+  /** Month fields: GET returning { earliest: "YYYY-MM-DD" }. List runs from that month through the current month. */
+  earliestMonthEndpoint?: string;
 }
 
 export type ReportResponseType = 'pdf' | 'excel';
@@ -322,7 +324,13 @@ export const REPORTS: ReportDefinition[] = [
     apiEndpoint: `${NEXT_PUBLIC_API_URL}/report/print-stock-lot-ledger`,
     responseType: "excel",
     fields: [
-      { label: "期間起 Period From（永遠該月1日）", name: "lastInDateStart", type: "date", required: true },
+      {
+        label: "期間起 Period From",
+        name: "lastInDateStart",
+        type: "month",
+        required: true,
+        earliestMonthEndpoint: `${NEXT_PUBLIC_API_URL}/report/stock-lot-ledger-earliest`,
+      },
       { label: "期間迄 Period To", name: "lastInDateEnd", type: "date", required: true },
       asyncItemCodeField(),
     ],
diff --git a/src/i18n/en/report.json b/src/i18n/en/report.json
index ea517d8e..b8ad8a2c 100644
--- a/src/i18n/en/report.json
+++ b/src/i18n/en/report.json
@@ -139,7 +139,7 @@
     "rep-020": {
       "title": "Stock Lot Ledger Report",
       "fields": {
-        "lastInDateStart": "Period From (always 1st of month)",
+        "lastInDateStart": "Period From",
         "lastInDateEnd": "Period To",
         "itemCode": "Item Code"
       }
diff --git a/src/i18n/zh/report.json b/src/i18n/zh/report.json
index 1c349ee5..c74e58e8 100644
--- a/src/i18n/zh/report.json
+++ b/src/i18n/zh/report.json
@@ -139,7 +139,7 @@
     "rep-020": {
       "title": "庫存流水帳報告",
       "fields": {
-        "lastInDateStart": "期間起（永遠該月1日）",
+        "lastInDateStart": "期間起",
         "lastInDateEnd": "期間迄",
         "itemCode": "貨品編號"
       }