Section 1326(a)(1) of the Bankruptcy Code provides:
Unless the court orders otherwise, the debtor shall commence making payments not later than 30 days after the date of the filing of the plan or the order for relief, whichever is earlier.
It is important to remember that your payment may be due before your meeting of creditors (also known as a 341 meeting). If it is, you should make sure you make your payment before then.