Tamaulipas → Coahuila · Autopista 40D Reynosa-Monterrey
On heavy-rain or dense-fog days the Reynosa, Tamaulipas, to Saltillo, Coahuila, leg routinely demands well more than the 3h 56m estimated: Autopista 40D Reynosa-Monterrey carries known hydroplaning hot spots and reduced-visibility corridors that justify dropping to 35 mph through a few short stretches. The outbound run covers 354 km (220 miles) over varied topography between Reynosa (the frontera con McAllen y polo maquilador del noreste fronterizo) and Saltillo (the capital coahuilense y centro de la industria automotriz Chrysler), demanding sharper attention on mountain descents and shoulder-less curves. Before pulling out, check brake-pad wear, tire tread depth, and washer-fluid level in the reservoir. Fuel spend holds near MXN 713.90 for the 29.5 liters (7.8 gallons) consumed. Even in adverse conditions, the flat tariff of MXN 6.50/km guarantees the standard outbound payout of MXN 2301.00 — log any incidental costs (extra toll, mandatory meal, emergency lodging) in a separate field on the Clara receipt. For the UK professional driving the 354 km (220 mi) between Reynosa and Saltillo, reimbursement of MXN 2301.00 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→Saltillo run must be reported via PAYE settlement agreement or it becomes a benefit-in-kind on the employee's tax code.