Understanding T-Bill Auctions

Introduction

Governments issue Treasury bills through regular auctions managed by their debt management offices. In the UK, the Debt Management Office (DMO) conducts weekly T-bill tenders.

Competitive vs Non-Competitive Bids

Auctions accept two types of bids. Competitive bids specify the yield the investor wants, and are filled from lowest yield upward until the issue is fully allocated. Non-competitive bids accept whatever yield the auction determines, guaranteeing allocation up to a size limit.

Retail investors typically participate via non-competitive bids through platforms like RetailBook, ensuring they receive an allocation at the market-clearing yield.

The Auction Cycle

1. 1. Announcement: DMO publishes tender details (size, maturity, dates)
2. 2. Bidding window: Investors submit orders (typically 1–2 days)
3. 3. Allocation: Bids ranked by yield, allocation confirmed
4. 4. Settlement: Payment collected and T-bills delivered (usually T+1)
5. 5. Maturity: Face value paid to holder at maturity date

What Determines the Yield?

T-bill yields are influenced by the Bank of England base rate, market expectations for future rate changes, overall demand from investors, and the government’s borrowing needs. In general, yields move in the same direction as the base rate.