Net sales is in division level but EBIT is in group level

Should I estimate also net sales in group level?

When EBIT (Operating Profit) is only in group level, it is perhaps not even worth of effort to follow either net sales in division level. Of course it gives you some guidance about the ability of the company to grow in the future: if some divisions/products are growing quickly and some are not, then the relative weight of the divisions is interesting information.

However, more interesting is to know how profitable the different divisions are. If you do not know it or you cannot even estimate it properly using the current information, then it is perhaps not worth of effort to follow either net sales at division level in a small company.

I would like to estimate sales in divisional level, what to do?

If you decide to follow the net sales in divisional level then:

Enter division names normally but add one extra "division" called Group (or Total etc.). Then use the actual divisions for net sales and the Group division for EBIT.

The only limitation is that you cannot estimate the Group division with EBIT-% (margin). However, you can avoid also this problem by writing formulas to the absolute cells: my EBIT estimate = my EBIT-% x total net sales. Otherwise you can use the model normally.