Nearly every company that adopts proper HR software started out on spreadsheets. That is not a mistake — for ten people, a spreadsheet covers the basics fine. The problem does not show up in year one. It shows up when someone needs to reconstruct what happened eight months ago, and the honest answer is «we don't know, it got overwritten».
Spreadsheets are not bad because they are spreadsheets. They are bad because they have no memory of what a cell looked like before the last edit. In HR, what a record looked like before the last edit is sometimes the only evidence you have in front of a labor inspector or an employee dispute.
What a cell can't do
Any cell can be overwritten by anyone with edit access, with no log of who changed which value or when. Compare that with how a real time-tracking system should behave: in Cantevia, correcting a clock-in never deletes the original entry — it annuls it and records who made the change and why, while the original timestamp stays visible forever. There's usually no way to limit who sees what in the sheet, either: anyone with access to the file sees every column, including personal data that should stay restricted to HR. That distinction matters a lot if Spain's labor inspectorate (the ITSS) ever asks for four years of records.
Silent duplication
When the same figure lives in several sheets — payroll, time off, attendance — someone has to copy it by hand between files, and every copy is a chance to get it wrong. This gets worse when several people edit the same file at once: two simultaneous edits can silently overwrite each other, and neither person finds out until days later. Overtime pay is a good example: the hourly rate should always come from annual gross salary divided by 1,792 hours. Type that number into a different cell every month and, sooner or later, it drifts from reality.
When spreadsheets stop being enough
Watch for these signals: more than one person edits the same file, you need to cross-reference attendance data against payroll, you have several absence types with different approval rules, or an inspection request lands and you can't hand over a clean, ordered history.
The real cost of an error copied by hand
A single-cell error doesn't stay in that cell. If a month's overtime hours get copied incorrectly from a spreadsheet into payroll, the mistake carries through to that person's actual pay, and fixing it means a corrected payslip, an explanation, and sometimes a tax adjustment. The more intermediate sheets sit between the original data and the payslip, the more chances something gets lost in the copy.
Spreadsheets stay the right tool for as long as the question is «how many vacation days does Maria have left». The moment the question becomes «who approved this, when, and why», it stops being a template problem and becomes a design problem.