Add total across sheets

Ahh. Yes, the great Indirect function. This will be your best friend to get this done.

https://help.apple.com/functions/mac/9.1/#/ffa596db0e

You will want to create a sheet that is essentially your "Review" or "Summary of Sheets" sheet. You'll add a table, and then you'll have a column where you will name each Sheet in your document. In an adjacent column, you'll use Indirect to reference the cell address of the total from each sheet.

=INDIRECT(ADDRESS(ROW, COLUMN,,,SHEET NAME&"::"&TABLE NAME))

Then just do a Sum of the Column of the Index, and you've got an on-going, running template that automatically updates itself as you add rows.

So, this solution is not completely congruent to excel (very few complex solutions are), but at the moment it's a workable solution that I believe will help you as you continue to flesh out your new workflow (changing from excel to numbers will likely necessitate some change even if minor).

Create a Table of contents, or Index Table for all your invoices. Keep it simple. Put Months on Header Row, Companies you created invoices for in the corresponding month in rows below. Then create a separate table for the totals only and use the same formula in discussion prior to tell the cell where to get the total. For example,

NOTA BENE: You must name the table the exact same as you are naming the corresponding sheet as follows.

Voila. Simply continue to add the company names in your table of contents table as you add invoices and your set.

I would recommend to duplicate your sheets to create new invoices, but honestly its up to you as long as the table names and position of the invoice total remains consistent.

There's several ways to organize your "Summary of Sheets" sheet, so play around with it and make it work for you however you think is most beneficial. Hope this is helpful.

When I add a new month in excel, because it is added between the blank ‘start’ and ‘end’ sheets, the total (or in your example, summary) sheet adds it automatically.

Not sure how you are doing this in Excel. I tried doing what you describe.

In any case, Numbers does not have the capability, if I understand correctly what you are trying to do.

SG

So my original answer is ultimately scalable, but yes, requires some planning in advance. Also, I'm not entirely sure how you're organizing your spreadsheet because it sounds like you're referring to sheets and tables almost interchangeably, but they are two distinct objects in a document, and you must keep that in mind when you build out your summary tables.

If you are adding multiple invoices to a sheet (meaning you have multiple tables in a sheet), then I would recommend to separate your summary table into two tables, one that is looking at sheets (which should be labeled as months based on your description) and another table that has the max number of invoices you might generate in a given month, and you'll want to name each Table you are creating the invoice for (make it generic like "Invoice 1, Invoice 2, etc). You can then continue to use the "Indirect(Address...)) formula to scale your summary sheet without doing additional work each time you had a table to a sheet (an invoice to a sheet).

The most important part of engineering a spreadsheet is to fully understand the problem, which I will admit going on the information you provided that I may not fully grasp what you're trying to do.

Posting screenshots, or links to your document will help us get a better picture of what you're trying to solve for and how you've constructed your current solution so we know how to offer help.

I would recommend you duplicate your document and anonymize the invoices if you're going to post a link, by the way. Good luck.