Switzerland’s largest bank UBS could face a fine of up to $6.3 billion if found guilty in a French investigation into whether it helped wealthy customers there avoid tax, a Swiss newspaper reported on Friday. A French court has already ordered UBS to deposit a 1.1 billion-euro ($1.4 billion) guarantee to cover a portion of potential fines in the case, but Swiss newspaper Le Temps said it had seen a legal document showing the bank could face a penalty of up to 5 billion euros.