Avoiding Calculation Errors

When using Exl-Plan, it is important to ensure that no calculation errors arise; that its sub-models produce identical results; and that no imbalances occur in the opening or projected balance sheets.

Because Exl-Plan does not use floating values to forceably balance its balance sheets, it is very sensitive to formulae errors and consequently all structural changes to the model must be applied correctly. For example, if an additional cashflow-related item is introduced into the model as an assumption row, changes may be needed in the income statement, cashflow and balance sheet output reports. See Making Complex Changes.

Exl-Plan displays on-screen messages when it detects calculation errors when the F9 function key, *Tools/Setup > Calculate All & Check menu command or "C" toolbar button are used. These messages (see below) cover the most likely error situations. The following general procedure should help locate and eliminate errors:

1.	Scan the rows showing CHECK balance sheets balance immediately below the Balance Sheets for imbalances. Make sure that the opening balance sheet balances correctly. If it does not show a zero opening balance at the third decimal place, review all the values entered for the opening balance sheet.

2.	Check the right-hand column of the Check Balances Report in the Check worksheet (*Output > Check) for any differences between the key values computed by Exl-Plan's sub-models.

3.	If necessary, save the model with a new file name. Then, locate the source of the error by progressively removing all assumption values and recalculating using the *Tools/Setup > Calculate All & Check menu command or "C" toolbar button.

4.	If the error cannot be located or easily fixed, the best option may be to revert to an error-free backup copy of the model.

The following messages will be displayed immediately after Exl-Plan recalculates if a calculation error is detected. Errors will only be reported if they are outside pre-set tolerance limits as Exl-Plan automatically filters out and ignores trivial errors due to rounding off and calculation differences etc. arising after the third decimal place.

Exl-Plan was extensively tested during its development to ensure that it is robust and does not contain or cause any errors. It was tested with zero values throughout to eliminate divide by zero errors; with large values for every assumption to test for possible imbalances between the sub-models; and with values entered and calculated on a progressive basis to detect errors caused by the interaction between variables. All Exl-Plan's calculations and formulae were checked manually and the entire model was extensively checked using an auditing system. Notwithstanding this, PlanWare - Invest-Tech cannot guarantee that all possible errors or sources of error have been removed and cannot anticipate errors that may be introduced by users. Accordingly, users should always review the output reports for possible anomalies and calculation errors. In some circumstances, values may not appear to add up correctly due to rounding off.