1diff --git a/DOCS.md b/DOCS.md
  2index 84b2980..f6cffd6 100644
  3--- a/DOCS.md
  4+++ b/DOCS.md
  5@@ -540,6 +540,20 @@
  6 @returns {number} 
  7 @constructor
  8 ```
  9+
 10+### PPMT 
 11+
 12+```
 13+  Returns for a given period the payment on the principal for an investment that is based on periodic and constant payments and a constant interest rate. 
 14+@param rate - The periodic interest rate. 
 15+@param period - The amortization period. 
 16+@param periods - The total number of periods during which the annuity is paid. 
 17+@param present - The present value in the sequence of payments. 
 18+@param future - [OPTIONAL] - The desired future value. Defaults to 0. 
 19+@param type - [OPTIONAL] - Indicates how the year is to be calculated. 0 indicates payments are due at end of period, 1 indicates payments are due at beginning of period. Defaults to 0. 
 20+@returns {number} 
 21+@constructor
 22+```
 23 ## Info
 24 
 25 
 26diff --git a/TODO.md b/TODO.md
 27index 5de4a06..a1779a2 100644
 28--- a/TODO.md
 29+++ b/TODO.md
 30@@ -102,7 +102,6 @@ Many of these formulas can be written by allowing the Sheet and Parser to return
 31 * ROMAN
 32 * SEARCH
 33 * SEARCHB
 34-* SPLIT
 35 * SUBSTITUTE
 36 * TEXT
 37 * VALUE
 38@@ -124,7 +123,6 @@ Many of these formulas can be written by allowing the Sheet and Parser to return
 39 * DURATION
 40 * FVSCHEDULE
 41 * INTRATE
 42-* PPMT - Similar to PMT, which is already written.
 43 * PRICE
 44 * PRICEDISC
 45 * PRICEMAT
 46diff --git a/dist/Formulas/AllFormulas.js b/dist/Formulas/AllFormulas.js
 47index 282528e..16a8de3 100644
 48--- a/dist/Formulas/AllFormulas.js
 49+++ b/dist/Formulas/AllFormulas.js
 50@@ -135,6 +135,7 @@ exports.MIRR = Financial_1.MIRR;
 51 exports.IRR = Financial_1.IRR;
 52 exports.IPMT = Financial_1.IPMT;
 53 exports.FV = Financial_1.FV;
 54+exports.PPMT = Financial_1.PPMT;
 55 var Statistical_1 = require("./Statistical");
 56 exports.AVERAGE = Statistical_1.AVERAGE;
 57 exports.AVERAGEA = Statistical_1.AVERAGEA;
 58diff --git a/dist/Formulas/Financial.js b/dist/Formulas/Financial.js
 59index ca58c42..7857908 100644
 60--- a/dist/Formulas/Financial.js
 61+++ b/dist/Formulas/Financial.js
 62@@ -675,3 +675,33 @@ var IPMT = function (rate, period, periods, present, future, type) {
 63     return interest * rate;
 64 };
 65 exports.IPMT = IPMT;
 66+/**
 67+ * Returns for a given period the payment on the principal for an investment that is based on periodic and constant
 68+ * payments and a constant interest rate.
 69+ * @param rate - The periodic interest rate.
 70+ * @param period - The amortization period.
 71+ * @param periods - The total number of periods during which the annuity is paid.
 72+ * @param present - The present value in the sequence of payments.
 73+ * @param future - [OPTIONAL] - The desired future value. Defaults to 0.
 74+ * @param type - [OPTIONAL] - Indicates how the year is to be calculated. 0 indicates payments are due at end of
 75+ * period, 1 indicates payments are due at beginning of period. Defaults to 0.
 76+ * @returns {number}
 77+ * @constructor
 78+ */
 79+var PPMT = function (rate, period, periods, present, future, type) {
 80+    ArgsChecker_1.ArgsChecker.checkLengthWithin(arguments, 4, 6, "PPMT");
 81+    rate = TypeConverter_1.TypeConverter.firstValueAsNumber(rate);
 82+    period = TypeConverter_1.TypeConverter.firstValueAsNumber(period);
 83+    if (period < 1) {
 84+        throw new Errors_1.NumError("Function PPMT parameter 2 value is " + period + ", but should be greater than or equal to 1.");
 85+    }
 86+    periods = TypeConverter_1.TypeConverter.firstValueAsNumber(periods);
 87+    if (periods <= 0) {
 88+        throw new Errors_1.NumError("Function PPMT parameter 3 value is " + periods + ", but should be greater than 0.");
 89+    }
 90+    present = TypeConverter_1.TypeConverter.firstValueAsNumber(present);
 91+    future = (typeof future === 'undefined') ? 0 : TypeConverter_1.TypeConverter.firstValueAsNumber(future);
 92+    type = (typeof type === 'undefined') ? 0 : TypeConverter_1.TypeConverter.firstValueAsNumber(type);
 93+    return PMT(rate, periods, present, future, type) - IPMT(rate, period, periods, present, future, type);
 94+};
 95+exports.PPMT = PPMT;
 96diff --git a/src/Formulas/AllFormulas.ts b/src/Formulas/AllFormulas.ts
 97index 1e65db2..3b4c70a 100644
 98--- a/src/Formulas/AllFormulas.ts
 99+++ b/src/Formulas/AllFormulas.ts
100@@ -138,7 +138,8 @@ import {
101   MIRR,
102   IRR,
103   IPMT,
104-  FV
105+  FV,
106+  PPMT
107 } from "./Financial";
108 import {
109   AVERAGE,
110@@ -447,5 +448,6 @@ export {
111   TYPE,
112   COLUMN,
113   ROW,
114-  T
115+  T,
116+  PPMT
117 }
118\ No newline at end of file
119diff --git a/src/Formulas/Financial.ts b/src/Formulas/Financial.ts
120index de4757e..9f826c3 100644
121--- a/src/Formulas/Financial.ts
122+++ b/src/Formulas/Financial.ts
123@@ -685,6 +685,37 @@ var IPMT = function (rate, period, periods, present, future?, type?) {
124   return interest * rate;
125 };
126 
127+
128+/**
129+ * Returns for a given period the payment on the principal for an investment that is based on periodic and constant
130+ * payments and a constant interest rate.
131+ * @param rate - The periodic interest rate.
132+ * @param period - The amortization period.
133+ * @param periods - The total number of periods during which the annuity is paid.
134+ * @param present - The present value in the sequence of payments.
135+ * @param future - [OPTIONAL] - The desired future value. Defaults to 0.
136+ * @param type - [OPTIONAL] - Indicates how the year is to be calculated. 0 indicates payments are due at end of
137+ * period, 1 indicates payments are due at beginning of period. Defaults to 0.
138+ * @returns {number}
139+ * @constructor
140+ */
141+var PPMT = function (rate, period, periods, present, future?, type?) {
142+  ArgsChecker.checkLengthWithin(arguments, 4, 6, "PPMT");
143+  rate = TypeConverter.firstValueAsNumber(rate);
144+  period = TypeConverter.firstValueAsNumber(period);
145+  if (period < 1) {
146+    throw new NumError("Function PPMT parameter 2 value is " + period + ", but should be greater than or equal to 1.");
147+  }
148+  periods = TypeConverter.firstValueAsNumber(periods);
149+  if (periods <= 0) {
150+    throw new NumError("Function PPMT parameter 3 value is " + periods + ", but should be greater than 0.");
151+  }
152+  present = TypeConverter.firstValueAsNumber(present);
153+  future = (typeof future === 'undefined') ? 0 : TypeConverter.firstValueAsNumber(future);
154+  type = (typeof type === 'undefined') ? 0 : TypeConverter.firstValueAsNumber(type);
155+  return PMT(rate, periods, present, future, type) - IPMT(rate, period, periods, present, future, type);
156+};
157+
158 export {
159   ACCRINT,
160   CUMPRINC,
161@@ -704,5 +735,6 @@ export {
162   MIRR,
163   IRR,
164   IPMT,
165-  FV
166+  FV,
167+  PPMT
168 }
169\ No newline at end of file
170diff --git a/tests/Formulas/FinancialTest.ts b/tests/Formulas/FinancialTest.ts
171index 9ca7207..f15617c 100644
172--- a/tests/Formulas/FinancialTest.ts
173+++ b/tests/Formulas/FinancialTest.ts
174@@ -17,7 +17,8 @@ import {
175   MIRR,
176   IRR,
177   IPMT,
178-  FV
179+  FV,
180+  PPMT
181 } from "../../src/Formulas/Financial";
182 import {
183   DATE
184@@ -437,4 +438,25 @@ test("FV", function() {
185   catchAndAssertEquals(function() {
186     FV.apply(this, [0.025, 1]);
187   }, ERRORS.NA_ERROR);
188+});
189+
190+
191+test("PPMT", function() {
192+  assertEquals(PPMT(0.025, 4, 24, 50000, 0, 1), -1623.8890945416422);
193+  assertEquals(PPMT(0.010, 3, 24, 33000, 0, 1), -1235.6588292014105);
194+  assertEquals(PPMT(0, 3, 24, 33000, 0, 1), -1375.00);
195+  assertEquals(PPMT(0, 3, 24, 0, 0, 1), 0);
196+  assertEquals(PPMT(0, 1, 3, 100, -1000, 1), 300);
197+  catchAndAssertEquals(function() {
198+    PPMT(0, 0, 24, 33000, 0, 1)
199+  }, ERRORS.NUM_ERROR);
200+  catchAndAssertEquals(function() {
201+    PPMT(0, 4, 0, 33000, 0, 1)
202+  }, ERRORS.NUM_ERROR);
203+  catchAndAssertEquals(function() {
204+    PPMT.apply(this, [0, 4, 0]);
205+  }, ERRORS.NA_ERROR);
206+  catchAndAssertEquals(function() {
207+    PPMT.apply(this, [0, 4, 0, 4000, 1, 1, 1]);
208+  }, ERRORS.NA_ERROR);
209 });
210\ No newline at end of file
211diff --git a/tests/SheetFormulaTest.ts b/tests/SheetFormulaTest.ts
212index 0087a24..90c9d1c 100644
213--- a/tests/SheetFormulaTest.ts
214+++ b/tests/SheetFormulaTest.ts
215@@ -882,6 +882,10 @@ test("Sheet T", function(){
216   assertFormulaEquals('=T("str")', "str");
217 });
218 
219+test("Sheet PPMT", function(){
220+  assertFormulaEquals('=PPMT(0, 3, 24, 33000, 0, 1)', -1375.00);
221+});
222+
223 test("Sheet *", function(){
224   assertFormulaEquals('= 10 * 10', 100);
225   assertFormulaEquals('= 10 * 0', 0);