Under Section 19 of the Limitation Act, 1963, what happens when a debtor makes a part payment of a principal debt before the expiration of the limitation period? 

Section 19(1) provides: "Where a person liable to pay a debt or legacy acknowledges it in writing on account of the debt or of interest on the legacy, before the expiry of the prescribed period, a fresh period of limitation shall be computed from the date of such acknowledgment." This provision encourages debtors to make part payments or acknowledge debts, knowing it creates a fresh limitation period benefiting creditors. The payment must be acknowledged in writing and signed by the debtor or authorized agent. This resets the clock, giving creditors additional time. Under Section 19(2), the proviso requires that (except for interest payments before 1 January 1928) the acknowledgment of payment must appear in the debtor's handwriting or be signed by them.