Esta es mi primera publicación en esta comunidad, ya intenté encontrar mi respuesta y no tuve éxito :(.
Estoy trabajando en una manera de entender la fórmula detrás de un préstamo que le permite al cliente pagar extra la misma cantidad mensual dos veces al año sin aumentar los intereses, una opción que funciona con pagos flexibles en algunos bancos y común en lugares como Perú.
Un ejemplo (tomado de un programa de amortización real):
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| # | Date | Month | Payment | Amortization | Interests | Balance | Comment |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 1 | 2015-04-30 | Apr | 2,699.00 | -332.10 | 3,031.10 | 439,425.00 | First payment, usually different |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 2 | 2015-05-31 | May | 2,715.34 | 39.90 | 2,675.44 | 439,757.10 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 3 | 2015-06-30 | Jun | 2,711.25 | -53.40 | 2,764.65 | 439,717.20 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 4 | 2015-07-31 | Jul | 5,614.66 | 2,939.14 | 2,675.52 | 439,770.60 | Double payment |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 5 | 2015-08-31 | Aug | 2,708.01 | -127.38 | 2,835.39 | 436,831.46 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 6 | 2015-09-30 | Sep | 2,716.12 | 57.70 | 2,658.42 | 436,958.84 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 7 | 2015-10-31 | Oct | 2,716.14 | 58.08 | 2,658.06 | 436,901.14 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 8 | 2015-11-30 | Nov | 2,712.08 | -34.50 | 2,746.58 | 436,843.06 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 9 | 2015-12-31 | Dec | 5,615.47 | 2,957.55 | 2,657.92 | 436,877.56 | Double payment |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 10 | 2016-01-31 | Jan | 2,712.92 | -15.28 | 2,728.20 | 433,920.01 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 11 | 2016-02-29 | Feb | 2,716.97 | 76.95 | 2,640.02 | 433,935.29 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 12 | 2016-03-31 | Mar | 2,716.99 | 77.44 | 2,639.55 | 433,858.34 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 13 | 2016-04-30 | Apr | 2,712.96 | -14.37 | 2,727.33 | 433,780.90 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 14 | 2016-05-31 | May | 2,717.01 | 77.84 | 2,639.17 | 433,793.27 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 15 | 2016-06-30 | Jun | 2,712.98 | -13.95 | 2,726.93 | 433,717.43 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 16 | 2016-07-31 | Jul | 5,616.36 | 2,977.58 | 2,638.78 | 433,732.48 | Double payment |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
| 17 | 2016-08-31 | Aug | 2,713.84 | 5.55 | 2,708.29 | 430,753.80 | |
+----+------------+-------+----------+--------------+-----------+------------+----------------------------------+
Nota: en Perú calculan la mensualidad incluyendo el cargo del seguro de vida, resté los conceptos para simplificar (pero el resultado es una mensualidad no fija).
Entonces, mi problema es: necesito calcular un pago fijo mensual que permita dos pagos adicionales al año y esos sin aplicar intereses.
Por ejemplo, un préstamo a 30 años, tasa anual del 12 % y USD 1000, utilizando una hipoteca de amortización constante:
P = A / ((( 1 + i ) ^ n - 1 )/( i ( 1 + i ) ^ n ))
A = loan amount = 1,000
i = monthly rate = (( 1 + 12% ) ^ ( 1 / 12 ) - 1 ) = 0.00948879293
n = periods = 30 * 12 = 360
---
So, my payment (P) will be: USD 9.83 ~
Estoy buscando una estrategia matemática financiera que me permita pagar dos veces esos 10 dólares dos veces más al año (pagando el mismo interés en esos meses).
Si pago solo, funciona a las mil maravillas:
+--------------------------------------------------------------+
| Single Payment |
+-----+---------+---------+----------+--------------+----------+
| # | # Month | Payment | Interest | Amortization | Balance |
+-----+---------+---------+----------+--------------+----------+
| 0 | | | | | 1,000.00 |
+-----+---------+---------+----------+--------------+----------+
| 1 | 1 | 9.83 | 9.50 | 0.33 | 999.67 |
+-----+---------+---------+----------+--------------+----------+
| 2 | 2 | 9.83 | 9.50 | 0.33 | 999.34 |
+-----+---------+---------+----------+--------------+----------+
| 3 | 3 | 9.83 | 9.49 | 0.33 | 999.01 |
+-----+---------+---------+----------+--------------+----------+
| 4 | 4 | 9.83 | 9.49 | 0.34 | 998.67 |
+-----+---------+---------+----------+--------------+----------+
| 5 | 5 | 9.83 | 9.49 | 0.34 | 998.34 |
+-----+---------+---------+----------+--------------+----------+
| 6 | 6 | 9.83 | 9.48 | 0.34 | 997.99 |
+-----+---------+---------+----------+--------------+----------+
| 7 | 7 | 9.83 | 9.48 | 0.35 | 997.65 |
+-----+---------+---------+----------+--------------+----------+
| 8 | 8 | 9.83 | 9.48 | 0.35 | 997.30 |
+-----+---------+---------+----------+--------------+----------+
| 9 | 9 | 9.83 | 9.47 | 0.35 | 996.95 |
+-----+---------+---------+----------+--------------+----------+
| 10 | 10 | 9.83 | 9.47 | 0.36 | 996.59 |
+-----+---------+---------+----------+--------------+----------+
| 11 | 11 | 9.83 | 9.47 | 0.36 | 996.23 |
+-----+---------+---------+----------+--------------+----------+
| 12 | 12 | 9.83 | 9.46 | 0.36 | 995.87 |
+-----+---------+---------+----------+--------------+----------+
| ... | | | | | |
+-----+---------+---------+----------+--------------+----------+
| 355 | 7 | 9.83 | 0.54 | 9.29 | 47.72 |
+-----+---------+---------+----------+--------------+----------+
| 356 | 8 | 9.83 | 0.45 | 9.37 | 38.35 |
+-----+---------+---------+----------+--------------+----------+
| 357 | 9 | 9.83 | 0.36 | 9.46 | 28.88 |
+-----+---------+---------+----------+--------------+----------+
| 358 | 10 | 9.83 | 0.27 | 9.55 | 19.33 |
+-----+---------+---------+----------+--------------+----------+
| 359 | 11 | 9.83 | 0.18 | 9.64 | 9.69 |
+-----+---------+---------+----------+--------------+----------+
| 360 | 12 | 9.78 | 0.09 | 9.69 | 0.00 |
+-----+---------+---------+----------+--------------+----------+
Pero el doble pago obviamente produce un saldo negativo... Necesito que sea exactamente igual: llegar a cero en el último.
+-----------------------------------------------------------------+
| Double paying (july and december) |
+-----+---------+-----------+----------+--------------+-----------+
| # | # Month | Payment | Interest | Amortization | Balance |
+-----+---------+-----------+----------+--------------+-----------+
| 0 | | | | | 1,000.00 |
+-----+---------+-----------+----------+--------------+-----------+
| 1 | 1 | 9.83 | 9.50 | 0.33 | 999.67 |
+-----+---------+-----------+----------+--------------+-----------+
| 2 | 2 | 9.83 | 9.50 | 0.33 | 999.34 |
+-----+---------+-----------+----------+--------------+-----------+
| 3 | 3 | 9.83 | 9.49 | 0.33 | 999.01 |
+-----+---------+-----------+----------+--------------+-----------+
| 4 | 4 | 9.83 | 9.49 | 0.34 | 998.67 |
+-----+---------+-----------+----------+--------------+-----------+
| 5 | 5 | 9.83 | 9.49 | 0.34 | 998.34 |
+-----+---------+-----------+----------+--------------+-----------+
| 6 | 6 | 9.83 | 9.48 | 0.34 | 997.99 |
+-----+---------+-----------+----------+--------------+-----------+
| 7 | 7 | 19.65 | 9.48 | 10.17 | 987.82 |
+-----+---------+-----------+----------+--------------+-----------+
| 8 | 8 | 9.83 | 9.38 | 0.44 | 987.38 |
+-----+---------+-----------+----------+--------------+-----------+
| 9 | 9 | 9.83 | 9.38 | 0.45 | 986.93 |
+-----+---------+-----------+----------+--------------+-----------+
| 10 | 10 | 9.83 | 9.38 | 0.45 | 986.48 |
+-----+---------+-----------+----------+--------------+-----------+
| 11 | 11 | 9.83 | 9.37 | 0.46 | 986.03 |
+-----+---------+-----------+----------+--------------+-----------+
| 12 | 12 | 19.65 | 9.37 | 10.29 | 975.74 |
+-----+---------+-----------+----------+--------------+-----------+
| ... | | | | | |
+-----+---------+-----------+----------+--------------+-----------+
| 355 | 7 | 19.65 | -43.01 | 62.66 | -4,589.83 |
+-----+---------+-----------+----------+--------------+-----------+
| 356 | 8 | 9.83 | -43.60 | 53.43 | -4,643.26 |
+-----+---------+-----------+----------+--------------+-----------+
| 357 | 9 | 9.83 | -44.11 | 53.94 | -4,697.20 |
+-----+---------+-----------+----------+--------------+-----------+
| 358 | 10 | 9.83 | -44.62 | 54.45 | -4,751.65 |
+-----+---------+-----------+----------+--------------+-----------+
| 359 | 11 | 9.83 | -45.14 | 54.97 | -4,806.61 |
+-----+---------+-----------+----------+--------------+-----------+
| 360 | 12 | -4,852.27 | -45.66 | -4,806.61 | 0.00 |
+-----+---------+-----------+----------+--------------+-----------+
Eso en hojas de google, aquí .
¿Alguna idea? Realmente apreciaré la ayuda!
gracias de antemano
Logré calcular el pago único que dejó el saldo en cero :)
El truco era: calcular una proporción mensual, duplicar esa proporción en cada mes de pago doble, sumar todas esas proporciones y dividir el monto principal en eso.
Se necesitan dos iteraciones, ¡pero funciona bien! Todavía buscando una forma no iterativa ...
La proporción mensual: 1/(1+monthly rate)^period
, ej. el ultimo deberia ser 1/(1+0.00948879293)^360= 0.03337792393
. Dado que el último es de doble pago: 0.03337792393*2= 0.06675584786
.
Ya actualicé las fórmulas en la misma hoja de Google ( aquí ) y trabajaré en una solución lineal.
Como esto:
+──────+──────────+──────────────+────────+──────────+───────────+───────────────+──────────+
| # | # Month | Double pay? | Ratio | Payment | Interest | Amortization | Balance |
+──────+──────────+──────────────+────────+──────────+───────────+───────────────+──────────+
| 0 | | | | | | | 1,000.00 |
| 1 | 1 | FALSE | 0.99 | 8.46 | 9.50 | -1.04 | 1,001.04 |
| 2 | 2 | FALSE | 0.98 | 8.46 | 9.51 | -1.05 | 1,002.10 |
| 3 | 3 | FALSE | 0.97 | 8.46 | 9.52 | -1.06 | 1,003.16 |
| 4 | 4 | FALSE | 0.96 | 8.46 | 9.53 | -1.07 | 1,004.23 |
| 5 | 5 | FALSE | 0.95 | 8.46 | 9.54 | -1.08 | 1,005.32 |
| 6 | 6 | FALSE | 0.94 | 8.46 | 9.55 | -1.09 | 1,006.41 |
| 7 | 7 | TRUE | 1.87 | 16.91 | 9.56 | 7.35 | 999.06 |
| 8 | 8 | FALSE | 0.93 | 8.46 | 9.49 | -1.03 | 1,000.09 |
| 9 | 9 | FALSE | 0.92 | 8.46 | 9.50 | -1.04 | 1,001.13 |
| 10 | 10 | FALSE | 0.91 | 8.46 | 9.51 | -1.05 | 1,002.19 |
| 11 | 11 | FALSE | 0.90 | 8.46 | 9.52 | -1.06 | 1,003.25 |
| 12 | 12 | TRUE | 1.79 | 16.91 | 9.53 | 7.38 | 995.87 |
| ... | | | | | | | |
| 355 | 7 | TRUE | 0.07 | 16.91 | 0.62 | 16.29 | 49.28 |
| 356 | 8 | FALSE | 0.03 | 8.46 | 0.47 | 7.99 | 41.29 |
| 357 | 9 | FALSE | 0.03 | 8.46 | 0.39 | 8.06 | 33.23 |
| 358 | 10 | FALSE | 0.03 | 8.46 | 0.32 | 8.14 | 25.09 |
| 359 | 11 | FALSE | 0.03 | 8.46 | 0.24 | 8.22 | 16.87 |
| 360 | 12 | TRUE | 0.07 | 17.03 | 0.16 | 16.87 | 0.00 |
+──────+──────────+──────────────+────────+──────────+───────────+───────────────+──────────+
robert harvey
robert harvey
benjaroa
robert harvey
benjaroa
robert harvey
robert harvey
benjaroa
robert harvey
benjaroa
robert harvey
robert harvey
benjaroa
robert harvey
benjaroa