I think the most difficult issue is the difference in each country, because each country has different requirements in terms of currency. The date and time.It's quite difficult to verify the file.
I think the most difficult problems is the difference of each country. Because each country is different in terms of currency, date and time , it is quite difficult to detect various file.
I think the most difficult problem is the difference of each country. Because each country has difference in the currency, date and time, so it is quite difficult to to check the files.