Tally marks are a variation of the unary numeral system. They are a form of numeral used for counting. They allow updating written intermediate results without erasing or discarding anything written down.

In Europe and the United States, tally marks are written as groups of five lines. The first four lines are vertical, and the fifth line runs diagonally across the first four.

Chinese, Korean and Japanese tally marks use the five strokes of 正.

Notched sticks, known as tally sticks also were used for this purpose. The burning of discarded tally sticks resulted in the Burning of Parliament.