The 11-digit birth number (rodné číslo) is used by Czech citizens and residents for filing taxes, banking, insurance, and similar purposes. The system, which dates back to 1954, uses a person’s date of birth and gender as a basis. The first two digits indicate the last two digits of the year of birth, the second two digits indicate the month of birth, which is increased by 50 for women, and the third two digits indicate the day of birth. A four-digit ending distinguishes people born on the same day.