in one year
1 + (23/100) = (1 + x)^12
1 + 0.23 = (1 + x)^12
(1 + x)^12 = 1.23
1 + x = 1.23^(1/12)
x = 1.23^(1/12) - 1
x =~ 0.017400841772181508280113627030242
That's about 1.74% per month (which is about 20.881% per year), compounded monthly, to equal 23% per year, compounded annually.
So I believe you can write
I=(1+.0174)12torI=1.017412t
