How to calculate compounding?

I would like to calculate interest on my savings account for each month (type of savings account) with compounding of interest.

Annual rate is 5.25%

Bank calculates this as follows:

14,000euro * 5,25 % / 365 days = 2,01euro * 30 days = 60,41euro -19 % tax = 48,93euro
48,93 is my interest after tax per month.

What I want to do is to calculate it in excel. Trouble is, that after subtracting the 19% tax I cannot add it back to the principal.
I mean I have the formula, it will lead me to 60,41euro but when I try to do +(A4) [to add the principal], it gives me ###

- Could you have a look and advise please ?

=(A4)*(B5/365)*30-(1-0.019)+(A4)

A4 = 14000
B5 = 5.25%
than / 365 * 30 - 19% +principal

Originally Posted by shg

=a4 * (1 + b5/365 * 30 * (1-19%))

Thanks! Works great.
Could you explain me why you used 1 + at the beginning ? I'm trying to learn how to do it myself in the future.