Sales tax compliance in Pakistan is a monthly discipline, not an annual event. Whether you're registered with FBR for goods or with PRA for services in Punjab, missing a month creates penalties, blocked input tax and audit exposure.
The core cycle is simple: issue proper tax invoices, record purchases with valid input tax, file the monthly return by the due date, and pay any liability. The businesses that get in trouble are usually the ones treating this as an afterthought.