# Calculating Interest Accrued for a late payment

I'm trying to calculate the interest accrued on my amortization schedule manually. I can calculate it fine if payments are exactly one month apart but this payment is More than 1 month apart.

This is a similiar question to Calculating Interest Accrued With an Uneven Interval but slightly different. That question asked when the duration is less than a month, I'm wondering what should happen if it's over a month, slightly.

Last transaction date is 2017-01-01

Next payment is on 2017-02-15 and interest accrued is 609.25 for this payment.

Details of loan

As of `2017-01-01 balance is \$100,000`

Compounding `Monthly`

Interest rate `5%`

May I ask how was 609.25 calculated?

I tried multiple approaches, first one is calculating 1 month + days left

1 month of interest accrued

``````accrued =  (((( 1 + (.05 / 12)) ^ 12)  ^ (1/12) - 1) * 100000)
= 416.67
``````

14 days left (using solution from the previous post)

``````\$100,000 * 0.05 * (14 / 365) = \$191.78
``````

Summing the two together gives me \$608.45 which is close but not quite correct.

Second approach I took is calculating daily interest accrued.

``````accrued =  (((( 1 + (.05 / 12)) ^ 12)  ^ (14/365) - 1) * 100000)
=  617.05
``````

The day count basis for accrued interest is actual/365.

May I ask what is the correct way to calculate the interest accrued.

The interest compounds monthly, so your balance after the missed payment includes the accrued interest for that period and should be `100,416.67`:
``````accrued =((((1+(0.05/12))^12)^(14/365)-1)*100416.67) + 416.67 = 609.03