# Paper trip log or GPS app in Portugal: what AT accepts in 2026

> Portugal's AT modernized mileage proof requirements. A side-by-side comparison of paper logs and GPS apps.

**Author:** Inês Pereira — Portuguese Tax Specialist (AT)  
**Published:** 2026-04-29  
**Updated:** 2026-04-29  
**URL:** https://quilometragem.com/blog/paper-trip-log-or-gps-app-in-portugal-what-at-accepts-in-2026

**TL;DR:** Portugal's AT accepts GPS apps since 2024 when they meet integrity, auditability, and reproducibility requirements.

- AT Despacho 1138/2024
- Hybrid (GPS + manual digital) is the most defensible
- Retain 4 years (6 with active inspection)
- GDPR/Law 58/2019 contract clause required

## Where the Portuguese rule stands

Portugal's AT requires every reimbursable trip to be documented with origin, destination, business purpose, kilometers, and vehicle. The classic format is the *boletim itinerário* (paper trip log). AT Despacho 1138/2024 explicitly recognizes digital support when it meets three conditions: data integrity (no post-record alteration), auditability (timestamps + actor on every change), and reproducibility for inspection. Modern GPS apps satisfy all three.

## Paper log weaknesses

Reconstructed from memory at week's or month's end, mileage estimated visually, folders lost, no timestamps to prove when entries were made. Inspections of teams >10 drivers, >1,500 km/month commonly find gaps.

## GPS app strengths

Real route, deterministic km, immutable timestamps, digital signature chain (driver + approver), exportable PDF/CSV with integrity hash. AT has been low-friction with companies using this stack since the 2024 Despacho.

## Where GPS fails

Forgot to start the trip (mitigate with auto-start by geofence), forgot to mark personal mode (mitigate with weekly approver review), drained battery (mitigate by accepting a digital manual form as complement). The hybrid stack — GPS for 90-95%, digital manual form for 5-10%, weekly approver — defends best.

## Retention

Keep mileage records for the general 4-year tax prescription window; 6 years if there are open inspections.

## Migration checklist

Choose an app that meets integrity + auditability + reproducibility, announce 30 days ahead, train approvers, run paper + GPS in parallel for 60 days, archive paper history as hashed PDFs, and update the internal policy and contract clause for location-data processing under Lei 58/2019 (Portugal's RGPD execution).

## Frequently asked questions

### Does a GPS app replace the paper log?

It can — provided it meets integrity, auditability, and reproducibility. Hybrid is more robust.

### How long to retain?

4 years (general prescription); 6 years if an inspection is open.

## Sources

- [Despacho AT 1138/2024 — Suporte digital para registos de quilometragem](https://www.portaldasfinancas.gov.pt/) — Autoridade Tributária e Aduaneira (2026-04-29)
- [Lei 58/2019 — Execução nacional do RGPD em Portugal](https://www.cnpd.pt/) — CNPD (2026-04-29)