diff --git a/docs/source/modeling.rst b/docs/source/modeling.rst
index 9d7929f..b340978 100644
--- a/docs/source/modeling.rst
+++ b/docs/source/modeling.rst
@@ -214,7 +214,8 @@ Bond
     * ``("originalBondBalance","A","B")`` -> bond balance at issuance of "A" and "B" 
     * ``("bondFactor",)``  -> bond factor
     * ``("bondDueInt","A","B")``  -> bond due interest for bond A and bond B
-    * ``("lastBondIntPaid","A")``  -> bond last paid interest
+    * ``("lastBondIntPaid","A")``  -> sum amount of last paid interest for bonds
+    * ``("lastBondPrinPaid","A")`` -> sum amount of last paid principal for bonds
     * ``("behindTargetBalance","A")``  -> difference of target balance with current balance for the bond A
     * ``("bondTxnAmt", None,"A")``  -> Total transaction amount of bond 'A'
     * ``("bondTxnAmt", "<PayInt:A>","A")``  -> Total transaction amount of interest payment bond 'A'
diff --git a/docs/source/nbsample/debug_sample.ipynb b/docs/source/nbsample/debug_sample.ipynb
index 9525f2c..15e7910 100644
--- a/docs/source/nbsample/debug_sample.ipynb
+++ b/docs/source/nbsample/debug_sample.ipynb
@@ -56,6 +56,34 @@
     "localAPI = API(EnginePath.DEV, lang='english',check=False)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "9560c303",
+   "metadata": {},
+   "source": [
+    "### Cashflow Debug Steps\n",
+    "\n",
+    "If user thinks something is off in the cashflow , here is couple steps to inspect \n",
+    "\n",
+    "1. Is Pool Cashflow Correct ?\n",
+    "   \n",
+    "   Please inspect \n",
+    "   \n",
+    "   `r['pool']['flow']`\n",
+    "\n",
+    "2. Is Waterfall Distribution Correct ?\n",
+    "\n",
+    "   Pls inspect accounts\n",
+    "\n",
+    "   `r['accounts']['<AccountName>']`\n",
+    "\n",
+    "3. Is fee paid correct ?\n",
+    "\n",
+    "   Pls inspect \n",
+    "\n",
+    "   `r['fees']['<FeeName>']`\n"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "dad1adb2",