Overview
========

This is a very simple utility that can show if it is cheaper to wait to be
paid after x number of days and possibly go into overdraft and pay interest
or if it would be better to get paid immediately by card but pay the merchant
service charge.


How it Works
============

To do this, it needs five pieces of information.

    1) The amount. This would be the amount of the invoice and the amount
       that you would be in overdraft and paying interest on.

    2) Interest Rate. The rate of interest you are charged by the bank on
       your overdraft. This will just be a yearly rate.

    3) Interest Type. This is how the bank calculates the interest. It will
       be one of two ways.

	* EAR. This is the Effective Annual Rate. It is defined as;

			r = (1 + i/n)^n - 1

	       Where i is the nominal rate (aka APR) and n is the
	       compounding frequency.

	* APR. This is the Annual Percentage Rate. This can be defined in
	       terms of the EAR as:

			r = n * ((1 + EAR)^(1/n) - 1)

	See do_calc() for how these are actually calculated.

    4) Payment Terms. This is how long it takes you to get paid in days.

    5) Merchant Service Charge. This is how much you'd be charged for card
       transactions. This is a one off percentage charge per transaction.

Given this information, it will then tell you how much interest you would
pay on the amount over the period given. It will also tell you what you'd
pay for the merchant service charge.

Lastly it will work out at what point the interest charges and merchant
service charge converge and give you this in days. For a given EAR it
can work this out exactly. For an APR it can approximate it to within a
day.


Caveats
=======

This will likely only work for UK banks. Also, it doesn't take into account
monthly charges for being in overdraft etc.

It doesn't do anything special with leap years.


Building / Running
==================

See INSTALL


License
=======

This application is licensed under the GNU General Public License version 2.
See COPYING