Tamaulipas → San Luis Potosí · Autopista 40D Reynosa-Monterrey
Before turning the key for San Luis Potosí, San Luis Potosí, out of Reynosa, Tamaulipas, run through the pre-trip checklist: registration card in the glovebox, current insurance card on your phone, working SunPass or E-ZPass transponder for the electronic toll plazas along Autopista 40D Reynosa-Monterrey, and a printed backup of the destination address in case GPS reception drops. The locked itinerary measures 646 km (401 miles) with an optimistic estimate of 7h 11m if cruise control sits steadily within the posted limit. Pulling out of Reynosa, the frontera con McAllen y polo maquilador del noreste fronterizo, the road eventually delivers you to San Luis Potosí, the capital potosina y nodo logístico que conecta el Bajío con el norte del país. Schedule departure outside the morning rush window and pack a thermos of coffee to skip an unscheduled stop in the first hundred miles. Budget around MXN 1301.96 just for the pump (53.8 liters / 14.2 gallons of gasolina Magna) plus headroom for tolls. Outbound reimbursement at MXN 6.50/km equals MXN 4199.00 cleared to the driver. Use the Clara generator the moment you park to wrap everything into a single digitally signed PDF. For the UK professional driving the 646 km (401 mi) between Reynosa and San Luis Potosí, reimbursement of MXN 4199.00 fits the subsistence allowance regime when paid at or below HMRC AMAP rates of 45p per mile for the first 10,000 business miles in the tax year. UK firms reimburse at HMRC AMAP rates (45p / 25p per mile) so the payment stays free of PAYE and NIC under approved mileage allowance payments rules. Retain a VAT receipt accepted by HMRC for input-tax recovery from the BEIS-tracked forecourt network forecourt used to refuel; His Majesty's Revenue and Customs (HMRC) compliance officers cross-reference fuel VAT receipts with the P11D return when reimbursement exceeds the approved rate. Excess paid above AMAP on the Reynosa→San Luis Potosí run must be reported via PAYE settlement agreement or it becomes a benefit-in-kind on the employee's tax code.