Simple IF Statement is not working (or I've lost my mind)

Can somebody help me, please?? I think I'm going mad!!

I have a ridiculously simple spreadsheet containing values and a running total.

I have written a simple IF statement to check that each total is correct.

This is showing an error on some rows when there is nothing wrong.

There is absolutely nothing complicated about this spreadsheet but I cannot for the life of me see what is happening!!

In order to investigate I have created data that demonstrates the problem (attached).

For example:

Result:

Value Total
40 32461.00 32768.02
41 -32461.00 307.02 ERROR but the total is correct
42 32461.01 32768.03
43 -32461.01 307.02
44 32461.02 32768.04
45 -32461.02 307.02
46 32461.03 32768.05

Showing formula for the same rows

40 32461 32768.02 =IF(C39+B40=C40,"","ERROR")
41 -32461 307.02 =IF(C40+B41=C41,"","ERROR")
42 32461.01 32768.03 =IF(C41+B42=C42,"","ERROR")
43 -32461.01 307.02 =IF(C42+B43=C43,"","ERROR")
44 32461.02 32768.04 =IF(C43+B44=C44,"","ERROR")
45 -32461.02 307.02 =IF(C44+B45=C45,"","ERROR")
46 32461.03 32768.05 =IF(C45+B46=C46,"","ERROR")

The problem only appears where there is a negative number in the value column and repeats in a strange pattern every 50 rows until it gets to row 61441 where it shows an error on every row with a negative number in the value column.

That worked a treat - thank you so much.

I can cancel the appointment with the shrink now.

... the article made for very interesting reading.

I was aware of the problems due to floating-point arithmetic but had not realised that this could affect a simple addition of negative numbers.

Thanks again.