Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Typically how many digits are in a cheque number? 
Checks are normally numbered sequentially, to keep them unique for record-keeping purposes. The check number takes as many digits as it takes, depending on how long the account has been open and thus how many checks have been written.  The most recent check I looked at had a four-digit number, but as has been pointed out businesses may run through thousands  per year. I recommend storing this in an unsigned long or long-long, which will probably be comparable to the bank's own limits. I don't know whether there is an explicit maximum value; we would need to find someone who knows the banking standards to answer that.