Portugal's ceiling for using your own car on business is 0,40 € per kilometre. It is current — Lei n.º 82/2023 (OE 2024) repealed the article that had held it at 0,36, restoring 0,40 from 1 January 2024, and half the Portuguese internet still quotes the old number.
But the harder question is not the digits. It is who is allowed to use them.
CIRS art. 33.º n.º 1 is explicit:
> «As remunerações dos titulares de rendimentos da categoria B, assim como (…) utilização de viatura própria ao serviço da atividade (…) não são dedutíveis»
A holder of category B income — an independent worker, a sole trader — cannot deduct paying themselves for using their own car in the activity. Not at 0,40, not at any figure.
You deduct the actual costs of the vehicle, on the terms that apply to your regime — fuel, insurance, maintenance, depreciation, apportioned to business use. That is a different kind of record: receipts and an apportionment, rather than a per-kilometre calculation.
The mileage record still matters, and arguably matters more, because the apportionment between business and private use is the number you have to be able to defend. But it is evidence for a percentage, not the basis of a per-kilometre claim.
Employees, reimbursed by an employer for using their own car on the employer's business. There the ceiling comes from Portaria n.º 1553-D/2008, and CIRS art. 2.º n.º 3 al. d) makes anything above it taxable as employment income.
The boletim itinerário — the mapa de deslocações — must show the reason for the journey, the places, the time spent, the objectives, and the daily or total allowance. Where an own car is used it must additionally identify the vehicle and its owner, the number of kilometres, the per-kilometre allowance and the total.
The owner is the field that goes missing. Naming the car is not the same as naming who owns it, and the map has to do both.
Nothing above requires software; a notebook does the job. What software changes is the failure mode — and for a sole trader working out an apportionment, the failure is not a missing trip but a missing denominator: the private driving that never gets written down, without which the business share is a guess.
DriveHub records every drive in the background, business and private, and asks afterwards which was which. That is the number the apportionment needs.
What it does not yet carry: an explicit purpose per row, and the vehicle's owner as distinct from the vehicle. Both the plate and the person appear in the report header.
This page quotes the CIRS articles by number so you can read them. It is not tax advice and does not know your situation — and this is a page about who a rule excludes, which is exactly the kind of question worth putting to a contabilista certificado before you file.
The full rule for Portugal, with the instruments it comes from: mileage log requirements in Portugal.