[urthos]

Jon from Splitwise here. Yep - we don't include interest rates or try to price debt transfers, because we want to keep things casual. The "debt simplification" is an awesome feature but is not on by default because some people have differing levels of trust with different friends.

We do send monthly reminders to make sure people are good about either paying back or picking up the check next time. People often just use it to keep track of who should pay next and that is the way I primarily use Splitwise personally. With good friends, Splitwise is just a way to let our balance roll and figure out who should pay today.

With more distant or very diligent friends who don't like being in debt, they settle up right away and like the monthly reminder emails. To each his or her own!

We have our API just for things like this. I actually have personally borrowed money with interest (a large amount to pay off a credit card) from a friend, and tracked the debt, payments, and interest on Splitwise. We did repayments via PayPal and I added interest each month using my own calculations. We were both very happy and it's been paid off for a while now.

If someone wrote a general Splitwise interest-on-your-balance app (I would make it be opt-in for friends who agreed, with 0% still as the default for balances) on our API, that'd be awesome.

[joshstrange]

Thanks Jon! When I get some free time I might play with the API a little bit. I'm sure flat interest % for balance at the end of the month (or any other point in time) would be fairly simple but I would want to take it a step further. I would like it have a "grace period" of X months (or X time intervals) from money lend date before interest kicks in and even then you would only be charged interest on money that hadn't been paid in X time intervals not all you owe. Of course this would be much more difficult than a simple:

    $interestBillAmount = $amountOwed*$interestRate

That ran each month. Anyways keep up the great work, I use Splitwise all the time and it's a huge time and stress saver!