Morten said:
I would like to have principal payments to be 0 in the first 12 (1-12)
periods and that the total payments in period 1-12 to just only reflect
the
interest payments (this means remaining balance to be the same also from
period 0-12). From period 13-360 you start to pay down on the loan.
Okay. Again, ignoring real-world issues (viz. rounding payments), the only
formulas that need to change are:
A12: =if(or(A11="",A11=$B$3),"",A11+1)
C11: =if(A11="","",if(A11<=$B$4,0,if(A11=$B$3,E10,$B$7)))
Copy C11 down through C370 to allow for up to 30 years (30*12 months).
Errata....
My previous formulas for total interest paid neglected to account for the
interest-only period. If you use the SUM formula, the above changes will
correct my omission automatically. If you use the "algebraic" formula, it
should be changed to:
=B4*B5 + C2*B6*(B1-B7*(B6-1)/2)
Addendum #1....
It occurred to me that you probably want to have the payment due date.
Ideally, that would be in column B, next to the payment number. But to
avoid confusion with my previous formulas, I will show it in column F.
F11: 5/31/2009 (payment #1 due date)
F12:
=IF(A12="","",min(date(year($F$11),A11+month($F$11),day($F$11)),eomonth($F$11,A11)))
Copy F12 down through F370.
The MIN expression ensures that: (a) if the first due date is the last day
of the month, all due dates are the last day of their respective months; and
(b) if the first due date is 29 or later, the due date is the last day of
any month with fewer days.
If EOMONTH causes a #NAME error, and you do not want "install" (enable) the
Analysis ToolPak, you can substitute the following:
date(year($F$11),A12+month($F$11),0)
Note that sometimes I use A11+MONTH(...), and other times I use
A12+MONTH(...). This is on purpose. A11+MONTH(...) is shorthand for
A12-1+MONTH(...).
Addendum #2....
The following model incorporates those pesky real-world issues caused by the
fact that a payment must be rounded to at least the lowest coin of the realm
(assumed to be 0.01). I will recap all of the formulas, although not all
are changed.
B1: 100000 (loan amount)
B2: 4.00% (annual interest rate; format as Percent
with 2 dp)
C2: =B2/12 (monthly interest rate; format as Percent
with 6 dp)
B3: 120 (loan term, months)
B4: 24 (interest-only term, months)
B5: =round(B1*C2,2) (interest-only pmt; format as Number with 2 dp)
B6: =B3-B4 (remaining term)
B7: =round(B1/B6,2) (principal pmt; format as Number with 2 dp)
For B5, note that I replaced ROUNDUP with ROUND. It is a small price to pay
for simplicity; see the formula for D11 below. Besides, it is closer to the
non-rounding template, which ignored the real-world issues, but used
formatting to display rounded numbers. (Note that rounding due to
formatting does not change the underlying number.)
E10: =B1
A11: 1
B11: =if(A11="","",round(C11+D11,2))
C11: =if(A11="","",if(A11<=$B$4,0,if(A11=$B$3,E10,$B$7)))
D11: =if(A11="","",round(E10*$C$2,2))
E11: =if(A11="","",round(E10-C11,2))
F11: 5/31/2009
A12: =if(or(A11="",A11=$B$3,round(n(E10),2)<=0),"",A11+1)
F12:
=IF(A12="","",min(date(year($F$11),A11+month($F$11),day($F$11)),eomonth($F$11,A11)))
Copy B11:E11 to B12:E12, then copy A12:F12 down through A370:F370 to allow
for up to 30 years (30*12 months).
The use of ROUND in B1 and E11 might seem redundant, considering the use of
ROUND in B7 and D11. Nonetheless, it is prudent to round B1 and E11 in
order to avoid propagating "numerical abberations" that creep into
expressions involving numbers with decimal fractions. The "numerical
abberations" arise because of the methods that Excel uses internal, viz.
standard binary floating-point representation and arithmetic.
The third condition in A12 -- ROUND(N(E10),2)<=0, ostensibly testing the
previous balance for zero -- covers the case when the principal payment (B7)
is rounded to a larger denomination, potentially causing the loan to paid
off sooner. Some lenders round the payment to an even dollar, for example.
The N() function covers for the fact that ROUND does not tolerate a text
parameter (notably the null string, "") as some functions do :-(.
Note that due to rounding of periodic amounts, the total interest can no
longer be computed the "algebraic" formula that I posted previously and
corrected above. The SUM formula should work just fine. But again, it
would be prudent to round the result, namely: ROUND(SUM(D11
370),2).
HTH.
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