Khata (credit ledger)

A khata is the shopkeeper's book of credit: each regular's purchases on account, what they have paid back, and what is still outstanding. Kept well, it holds loyal customers; kept loosely, it quietly ties up the cash the shop needs for stock.

Whether it lives in a notebook or an app, the habit that matters is the same — write every entry the moment it happens, and look at the totals every week.