xlsx

Place every assumption in its own labelled input cell, reference those cells in formulas like =B5*(1+$B$6), and copy one formula per row across all periods. Add a Checks sheet with tie-out formulas that evaluate TRUE, then finalize with the financial-model audit profile.

Open the file with the office tool and snapshot the relevant sheet to read its conventions, styles, and marked input cells. Write only into designated input cells, never overwrite existing formulas, and run the audit before and after your edit.

Prefer Excel-2007-era functions like SUMIFS, INDEX/MATCH, IFERROR, and SUMPRODUCT, which every engine evaluates. Avoid spill functions like XLOOKUP, FILTER, and UNIQUE in portable mode, since files written without spill metadata keep only the top-left value.

Finalize recalculates the workbook and blocks completion when any cell contains #REF!, #DIV/0!, #VALUE!, #NAME?, #N/A, or #NUM! errors. Fix the cells named in the error summary and finalize again; inherited errors must be resolved against the original baseline.

Yes, raw tabular files like .csv and .tsv are supported using set_range with a 2D values array and append_row. These formats carry no styles, formulas, or multiple sheets, and they do not require visual review.

Portable mode needs no Excel installation and preserves .xlsm macros without running them, but recalculation relies on LibreOffice. It refuses workbooks with external file links and cannot process spill functions, so use background mode with Microsoft Office for those cases.