Cash checks should be filled in with black pen and carbon ink.

1. The reason why black pen and carbon ink are used is because the water has evaporated and the carbon mark is still there, so it can't be faked, and it can be anti-counterfeiting. Archaeology relies on carbon to date.

2. Article 120 of the Measures for Payment and Settlement stipulates that cheques shall be filled in carbon ink or ink, unless otherwise stipulated by the People's Bank of China.

So the bank staff will ask you this. And because the check belongs to the archives kept by the bank, the storage period is 15 years. The People's Bank of China should make provisions on this in order to ensure that the original documents preserved are not faded and easy to query.