In Spain, almost every company outsources payroll filing and social security contributions to an external provider known as a gestoría — part accountant, part payroll agency. The real question is not whether HR software should replace that provider (it typically does not, and that is not what these platforms are built for), but whether HR should also run its own parallel calculation.
The answer comes down to something concrete: when the provider's monthly payroll document lands, does anyone actually check it line by line against what HR expected, or is it trusted blindly?
When it makes sense to run payroll inside your HR system
When each month's variable data — overtime, allowances, flexible benefits, absences — already lives in the HR system because that is where it gets approved, it makes sense for that same system to produce an estimated income tax and social security calculation per person. Cantevia does this with a monthly sheet (one row per employee, one column per configurable variable concept), and it treats company directors' income tax differently from general-regime employees: directors get a fixed rate under Spanish tax rules (with a reduction for smaller companies), while regular employees are taxed progressively. Mixing the two up is a common and costly mistake to fix after the fact.
Why this doesn't replace your payroll provider
The internal estimate is not the official payslip or the tax filing — that stays the provider's job. The provider remains responsible for filing social security contributions and withholdings with the tax authority; the internal calculation is only there to anticipate and verify, never to replace that filing. What the internal calculation adds is a way to compare the document that arrives each month against what HR expected to pay, before the gap turns into a real problem. If the provider applies a different tax rate than expected, or an allowance goes missing, it shows up that same month, not six months later at the next review.
When it's better to keep them separate
If the volume of variable pay concepts is minimal — payroll is mostly fixed, no overtime, no flexible benefits — building a parallel estimate can be more work than it is worth. In that case, it is enough for the HR system to hand over clean data — hours, absences, hires and departures — to the payroll provider, without needing an extra verification layer.
What happens if you never compare
The risk of never checking the provider's payslip against your own estimate isn't just one possible one-off error: it's having no way to spot a pattern, such as a concept that's systematically miscalculated every month, or someone whose tax rate changed and nobody updated it anywhere. Monthly comparison turns a problem that would only surface at an annual audit into something fixed the same month it happens.
The question is not «payroll inside HR software, yes or no» — it is whether this month's variable concepts are substantial enough to be worth checking before they arrive already invoiced.