San Luis Potosí → Guanajuato · Autopista 57D México-San Luis Potosí
Returning from San Luis Potosí, San Luis Potosí, back to Salamanca, Guanajuato, the itinerary retraces the same 222 km (138 miles) of the outbound segment, predominantly via Autopista 57D México-San Luis Potosí, adding another 2h 28m to the corporate odometer. Unlike the outbound leg, the homeward journey is usually executed at the close of the business day, when heavy truck traffic, accumulated fatigue, and dropping daylight all demand sharper focus. Anyone hoping to ease the arrival back into Salamanca, the sede de la refinería Ing. Antonio M. Amor de Pemex, may consider an overnight stop in a midpoint town and splitting the haul into two shorter stints. Fuel expense holds steady near MXN 447.70, totalling roughly 37.0 liters for the entire trip when added to the outbound segment. The return reimbursement reaches MXN 1443.00, doubling the aggregate payout for the full journey. Log each leg separately in the Clara receipt, with distinct timestamps, so the paperwork accurately mirrors the vehicle's actual movement. For the US professional driving the 222 km (138 mi) between San Luis Potosí and Salamanca, reimbursement of MXN 1443.00 stays non-taxable to the employee when the employer follows an accountable plan under Treas. Reg. §1.62-2 and reimburses at or below the IRS standard mileage rate. US employers generally reimburse at the IRS standard mileage rate so the payment stays non-taxable to the employee under Pub. 463. Keep the IRS-compliant expense report (Form 1040 Schedule C, line 9) alongside the fuel receipt from any EIA-tracked retail station network pump used along the leg; Internal Revenue Service (IRS) examiners pull contemporaneous mileage logs first when auditing Schedule C unreimbursed business expenses, and the San Luis Potosí→Salamanca corridor must show date, business purpose, and odometer readings.