diff --git a/bms-back/bms-system/src/main/java/com/bms/ar/service/impl/ArBillServiceImpl.java b/bms-back/bms-system/src/main/java/com/bms/ar/service/impl/ArBillServiceImpl.java
index 48d831d6..8b095eef 100644
--- a/bms-back/bms-system/src/main/java/com/bms/ar/service/impl/ArBillServiceImpl.java
+++ b/bms-back/bms-system/src/main/java/com/bms/ar/service/impl/ArBillServiceImpl.java
@@ -1570,6 +1570,8 @@ public class ArBillServiceImpl implements IArBillService {
     private void writeOoxmlFooter(OutputStream output, Map<Integer, String> templateRows, int footerRow, ArBill bill)
             throws IOException {
         int rowOffset = footerRow - TEMPLATE_FOOTER_START_ROW;
+        int lastDetailRow = Math.max(TEMPLATE_DATA_START_ROW, footerRow - 1);
+        String totalAmountFormula = "SUM(S" + TEMPLATE_DATA_START_ROW + ":S" + lastDetailRow + ")";
         for (int offset = 0; offset < 4; offset++) {
             int sourceRowNumber = TEMPLATE_FOOTER_START_ROW + offset + 1;
             int targetRowNumber = sourceRowNumber + rowOffset;
@@ -1577,7 +1579,8 @@ public class ArBillServiceImpl implements IArBillService {
             if (offset == 0) {
                 row = replaceCellXml(row, "B" + targetRowNumber, "银行信息", false);
                 row = replaceCellXml(row, "P" + targetRowNumber, "本期应收金额", false);
-                row = replaceCellXml(row, "S" + targetRowNumber, bill.getTotalAmount(), true);
+                row = replaceFormulaCellXml(row, "S" + targetRowNumber, totalAmountFormula,
+                        nvl(bill.getTotalAmount()));
             } else if (offset == 1) {
                 row = replaceCellXml(row, "B" + targetRowNumber, "开户名", false);
                 row = replaceCellXml(row, "C" + targetRowNumber, bill.getBankAccountName(), false);
@@ -1587,7 +1590,9 @@ public class ArBillServiceImpl implements IArBillService {
                 row = replaceCellXml(row, "B" + targetRowNumber, "账号", false);
                 row = replaceCellXml(row, "C" + targetRowNumber, exportBankAccountNo(bill.getBankAccountNo()), false);
                 row = replaceCellXml(row, "P" + targetRowNumber, "本期未核销金额", false);
-                row = replaceCellXml(row, "S" + targetRowNumber, bill.getUnwrittenAmount(), true);
+                String unwrittenAmountFormula = "S" + (targetRowNumber - 2) + "-S" + (targetRowNumber - 1);
+                row = replaceFormulaCellXml(row, "S" + targetRowNumber, unwrittenAmountFormula,
+                        nvl(bill.getUnwrittenAmount()));
             } else {
                 row = replaceCellXml(row, "B" + targetRowNumber, "开户行", false);
                 row = replaceCellXml(row, "C" + targetRowNumber, bill.getBankName(), false);
@@ -1675,6 +1680,16 @@ public class ArBillServiceImpl implements IArBillService {
     }
 
     private String replaceCellXml(String rowXml, String reference, Object value, boolean numeric) throws IOException {
+        return replaceCellXml(rowXml, reference, value, numeric, null);
+    }
+
+    private String replaceFormulaCellXml(String rowXml, String reference, String formula, Number cachedValue)
+            throws IOException {
+        return replaceCellXml(rowXml, reference, cachedValue, true, formula);
+    }
+
+    private String replaceCellXml(String rowXml, String reference, Object value, boolean numeric, String formula)
+            throws IOException {
         if (rowXml == null) {
             throw new IOException("应收账单模板缺少行: " + reference);
         }
@@ -1694,6 +1709,9 @@ public class ArBillServiceImpl implements IArBillService {
             StringBuilder cell = new StringBuilder("<c").append(normalizedAttributes)
                     .append(" t=\"").append(numeric ? "n" : "inlineStr").append("\">");
             if (numeric) {
+                if (formula != null) {
+                    cell.append("<f>").append(xmlEscape(formula)).append("</f>");
+                }
                 cell.append("<v>").append(value == null ? "" : numberText((Number) value)).append("</v>");
             } else {
                 String text = value == null ? "" : String.valueOf(value);
@@ -1708,7 +1726,7 @@ public class ArBillServiceImpl implements IArBillService {
         }
         matcher.appendTail(result);
         if (!found) {
-            return insertMissingCellXml(rowXml, reference, value, numeric);
+            return insertMissingCellXml(rowXml, reference, value, numeric, formula);
         }
         return result.toString();
     }
@@ -1717,7 +1735,8 @@ public class ArBillServiceImpl implements IArBillService {
      * 兼容不同 Excel/WPS 版本保存后被省略的空单元格，按列顺序补回动态单元格。
      * C3/P3 使用模板中对应的样式，避免客户名称或账单周期单元格变成无边框样式。
      */
-    private String insertMissingCellXml(String rowXml, String reference, Object value, boolean numeric) throws IOException {
+    private String insertMissingCellXml(String rowXml, String reference, Object value, boolean numeric, String formula)
+            throws IOException {
         int rowEnd = rowXml.lastIndexOf("</row>");
         if (rowEnd < 0) {
             throw new IOException("应收账单模板缺少行结束节点: " + reference);
@@ -1739,9 +1758,11 @@ public class ArBillServiceImpl implements IArBillService {
             cell.append(" s=\"").append(style).append("\"");
         }
         if (numeric) {
-            cell.append(" t=\"n\"><v>")
-                    .append(value == null ? "" : numberText((Number) value))
-                    .append("</v></c>");
+            cell.append(" t=\"n\">");
+            if (formula != null) {
+                cell.append("<f>").append(xmlEscape(formula)).append("</f>");
+            }
+            cell.append("<v>").append(value == null ? "" : numberText((Number) value)).append("</v></c>");
         } else {
             String text = value == null ? "" : String.valueOf(value);
             cell.append(" t=\"inlineStr\"><is><t");