Mortgage modelling tool

Mortgage calculator and analysis tool (Netherlands)

version

toets hier voor Nederlands

Mortgage parameters:

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Input values

Input fields allow entering simple formulas using arithmetical espressions.
Example of a valid input: (1+2*3)/4
Most of the input values can be "tuned": hover mouse over and scroll up/down with Shift pressed
When pointed with a mouse - tooltip for the input values will display the field's variable name (used in other formulas).



Output values

Output values calculated automatically from input values (calculated fields are disabled for manual input)
When pointed with a mouse - tooltip for the field will show the field's variable name and calculation formula.



Payments Schedule

Calculated monthly mortgage repayment plan
total_payment = base_payment + extra_payment + extra_payment2 + penalty
base_payment = capital_payment + interest_amt (capital payment and interest amount values depend on the mortgage type)
extra_payment - additional montlhy repayments, topped up so that total_payment >= extra_payment_topup
extra_payment2 - additional periodic repayments.



Manual adjustments to payments Schedule

extra_payment values can be manually adjusted by clicking on the value in the payment schedule cell. Adjusted values "live" until any other parameters of the loan gets changed and loan gets recalculated.



House price

sell price of the house.
for "home ownership tax" (eigenwoningforfait) and for assets calculation - house value is used



Tax refund target

For Annuity and Linear types of mortgages - a portion of interest payed is tax deductible(hypotheekrenteaftrek)
tax refund target setting controls what happens to the tax benefit generated therefrom
0 - tax benefit is ignored as if it is not happening
1 - tax benefit is accrued as a "bonus" amount and summed up in "total tax refunded"
2 - tax benefit is used as an extra repayment towards principal debt (added to extra_payment)



"net" amounts

if tax refund target = 1 "net" values calculated by substracting tax benefits (hypotheekrenteaftrek) from "gross" amounts



Extra repayments

• There are several repayments that can be modelled:
[Mortgage] tab
• Monthly repayment
• Flexible periodic repayment: you can set period of the repayment (usually 12 months), first month of the repayment and repayment value
[Extra repayments] tab
• 2 additional flexible periodic repayments
• extra_payment_topup: every month an extra repayment will be made such that total payment is not less than this value
Settings
• Max. allowed yearly repayment sum - % from the original debt
• If total annual extra repayments amount surpass the max allowed threshold - surplus will be "taxed" by penalty %, and actual repayments made will be lower
• If penalty % is set to 100 - all extra repayments will be capped in such a way that no penalties occur



Asset dynamics

• Final (up to the loan's term) assets status calculated for two scenarios:
• Renting: monthly increment = salary - rent + yeary bonus (if the month is right), deposit rate is assumed for all current assets accumulated
• Housing: montlhy increment = salary - house ownership tax - loan payment (net) + yeary bonus (if the month is right), deposit rate assumed for all current assets accumulated, housing market rate assumed for the current estate (fraction) owned
Comparisons
• Housing / Renting - ratio of final assets for "housing" and "renting" scenarios
• Housing ROI = final housing final assets / total amount invested in the mortgage



Whatif analysis

• Mechanism to model parameters of the loan as a function of any other parameter (any parameter of the loan can be "tested")
"Variable1" and "Variable2": range descriptors for variables you'd like to "test". Format: variable_name(start_value, end_value, steps)
"Metrics" comma-separated list of expressions (using loan parameter names), - result of which you'd like to see on the plot. In a simpliest case - it is just a parameter name of interest (e.g. loan_term_actual)
• it is possible to use "original" mortgage parameter value expressions using _0 postfix (e.g. loan_term_actual_0).
• If only Variable1 is specified - all metrics will be plotted on the 2D.
• If both Variable1 and Variable2 specified - first metric in the list will be plotted on the 3D plot(surface)."
• Probing takes time (depend on the number of steps requested), probing launched by [Recalculate] button.
• After calculating all possible mortgages for the parameters set requestsd - the metric of interest (first metric in the list) will be drawn in the "What-if Graph" section below.



Interest rates

Overview
ABN Amro
ING
Rabo Bank


Modelling results:

This graph updated when you run "Recalculate" from "What-if" section above.
Source:
Github
Disclaimer:

The tool intended only for research purposes - use it at your own risk.

There is no guarantee for the quality and accuracy of the data provided.

Involve a qualified professional before making any decisions.