# Formula Validation when using Line Item Subset with SUM

Please implement the same validation rules when using SUM over a Line Items Subset as are present for using SUM over List dimensions.

Currently no error message is shown when creating a formula with SUM over an unneeded or incorrect Line Item Subset while an error message appears when doing the same for SUM over a List dimension. This issues allows users to submit invalid formulas when using Line Item Subsets which can impact our implementations negatively.

Here a model example:

**LISS definition: We define a standard Line Item Subset**

**2. Source Model: We define a source module we want to SUM over the "1" line item using the LISS dimension and the organization dimension.**

**3. Target Model: We define a target module with two line items for executing the respective SUMs.**

When summing over LISS the formula is taken without an error message - this is not correct.

When summing over organization Anaplan correctly creates an error prompt and does not take the formula:

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