Simple interactive statement/spreadsheet for savings account/loan

Kernel_Sanders

I am holding funds for my mother who has substantial savings awaiting transfer each month into her higher interest regular savings accounts (I have spare capacity in my own 2%+ accounts and she doesn't). I'd like my brothers to be able to see exactly what's going on though, so I'm looking for an online statement that I can update, and ideally would be accessible by them at any time. The nearest I've got is this offering from http://www.brothersoft.com/moneyline-personal-finance-software-512627.html
I'm able to enter all the info I need to show, but the thing has no facility to calculate the 2% p.a.daily interest that I will need at some point!

grumbler

If 2% is AER, then calculate the daily rate as 1.02^(1/365)-1.
Then either

• add the interest daily and recalculate the balance (or just multiply the previous balance by 1.02^(1/365) to get the new one)

OR

• do this only when deposits or withdrawals are made. For N days the interest is (starting balance)*(1.02^(N/365)-1). Or just (new_balance)=(starting_balance)*(1.02^(N/365)).

As simple as that.

colsten

Kernel_Sanders wrote: »

I'd like my brothers to be able to see exactly what's going on though, so I'm looking for an online statement that I can update, and ideally would be accessible by them at any time.

How will your brothers access the statement at any time?

Your software looks almost like a [more expensive] carbon copy of AceMoney, which I recently migrated to from MS Money. I couldn't find any obvious way to share the application with others - - unless they have access to my PC. It would be useful for me too if I could share my data over the Internet, so if you know how to do it, I would be grateful for some tips.

grumbler

A live google spreadsheet?
Or just a statement in a common format updated regularly in google docs?

masonic

grumbler wrote: »

If 2% is AER, then calculate the daily rate as 1.02^(1/365)-1.
Then either

• add the interest daily and recalculate the balance (or just multiply the previous balance by 1.02^(1/365) to get the new one)

OR

• do this only when deposits or withdrawals are made. For N days the interest is (starting balance)*(1.02^(N/365)-1). Or just (new_balance)=(starting_balance)*(1.02^(N/365)).

As simple as that.

1.02^(1/365)-1 would be the daily rate if interest was compounded daily, which is quite unlikely. More likely interest is paid and compounded either monthly or annually, in which case to get from AER to daily gross rate would be [1.02^(1/12)-1]*12/365 and 0.02/365 respectively. The general case is [(1+rate)^(1/n)-1]*n/365 where n is the number of times interest is paid per year.

Kernel_Sanders

masonic wrote: »

1.02^(1/365)-1 would be the daily rate if interest was compounded daily, which is quite unlikely. More likely interest is paid and compounded either monthly or annually, in which case to get from AER to daily gross rate would be [1.02^(1/12)-1]*12/365 and 0.02/365 respectively. The general case is [(1+rate)^(1/n)-1]*n/365 where n is the number of times interest is paid per year.

Indeed, when I wrote '2% p.a.daily interest' I meant interest calculated daily (but paid annually). I know how to work out interest (even without knowing what ^ means ), but I was hoping that the simple software required wouldn't be too much for a free program!

grumbler

masonic wrote: »

1.02^(1/365)-1 would be the daily rate if interest was compounded daily, which is quite unlikely.

I think not only it's not unlikely, but it's how it is calculated - on a daily basis. However for 2% the difference between 1.02^(1/365)-1 and (1.02^(1/12)-1)/(365/12) will be negligible: 0.005426% and 0.005430% accordingly.

More likely interest is paid and compounded either monthly or annually

And what if the balance changes during a month o a year?

masonic

grumbler wrote: »

Not only it's not unlikely, but it's how it is calculated - on a daily basis.

Yes interest is calculated on a daily basis, but it isn't compounded on a daily basis in pretty much any account available.

Paid and compounded daily: 1.02^(1/365)-1 is equal to 0.00542552% daily rate
Paid and compounded monthly: [1.02^(1/12)-1]*12/365 is equal to 0.00542986% daily rate
Paid and compounded annually: 0.02/365 is equal to 0.00547945% daily rate

And what if the balance changes during a month o a year?

The daily rate above is applied to the closing balance of the account each day.

That is the same as if you compound my daily rate for a month.

Close, but not equal. It is less close when interest is paid annually, but if you only want an estimate then the simpler 0.02/365, which gives the correct rate for annual interest, is still 99% accurate for monthly.

Kernel_Sanders

grumbler wrote: »

And what if the balance changes during a month o a year?

As it will, as excess money will be swept into it.
Without trying to be pedantic, you are both wrong if the annual interest is paid in a year's time because that year would be based on 366 days

grumbler

masonic wrote: »

Close, but not equal.

OK, I don't insist and edited my post already.
We agree that the difference is very small.

masonic

Kernel_Sanders wrote: »

Without trying to be pedantic, you are both wrong if the annual interest is paid in a year's time because that year would be based on 366 days

Well if you want to account for that, then you'll have to check your T&Cs. Some banks will pay you 366 days of interest in leap years, but others don't.