Excel SUM Function Development

I need a talented spreadsheet whiz to develop an Excel formula specifically to perform SUM calculations. This project involves sourcing data from multiple worksheets that unfortunately do not have a uniform structure. I have attached the spreadsheet. There is the base tab where I need all the formulas input plus there is a basic tax table plus there is a second tab within the spreadsheet that provides a home loan repayment schedule.

the basic requirement is for me to use the spreadsheet as a template for many similar scenarios. I need each column to be able to include figures from previous column.


Ideal Skills:
- Solid understanding of Excel formulas, specifically SUM
- Familiarity with handling inconsistent data structures across multiple worksheets
- Proficient in Excel data processing and manipulation
- Detail-oriented and meticulous with calculations

Your primary task will be to:
- Develop numerous SUM formula in Excel
- Line /Column formula Requirements are advised
- Source data from same plus another worksheet with different structures for calculations plus a tax calculation

In brief, this is a project for a person with a solid knowledge of column formulas including various ongoing base variables in Excel