Hi, so I'm working on a physical inventory procedure for my internship (business accounting major), since we have lots of different products, assets and such in inventory and it's a bit of a mess.

Right now the idea is to make a count of a percentage of the total inventory each month, then make a total count at year end if it seems necessary. Problem is, I'd like to take the percentage each month from the whole thing, including what was already counted, to get an hopefully statistically significant view of the thing each month. I know it makes sence from an accounting point of view, but I have no idea how the math works.

Basically, I'd like to know what percentage of the total to take each month to reasonably sure that a large part (say 85%) of the assets have been counted come year end.

Thanks.