IMLA said the new publications are designed to help bridge any knowledge gap on how mortgages are priced.

The importance of swap rates was highlighted in early 2026 following the outbreak of conflict involving the US, Israel and Iran. Between early March and early May, two-year swap rates rose from around 3.6% to more than 4.5%.

Over the same period, average two-year fixed mortgage rates increased from 3.97% to 5.14%. That represented a rise of more than 1.1 percentage points. Tracker mortgage rates, which follow Bank Rate directly, were unaffected.

The main report, How Lenders Fund Fixed-Rate Mortgages: Swap Rates Explained, was written by Rob Thomas, principal researcher at IMLA and a former Bank of England economist.

The report explains how lenders fund fixed-rate mortgages. It outlines the role of deposits and other variable-rate funding sources. It also examines how the swap market allows lenders to offer fixed-rate products and why changes in swap rates can lead to rapid repricing.

A second publication, Swap Rates Explained: A Five-Minute Read, provides a shorter summary. It is designed for advisers who need a simple explanation for client conversations.

Kate Davies, executive director of IMLA, said: “Swap rates have become part of the everyday language of the mortgage market, yet they remain poorly understood outside a relatively small group of specialists.

“When mortgage rates rise or products are withdrawn, borrowers want answers. Advisers need to be able to explain what is happening.

“The key point is that fixed-rate mortgage pricing follows swap rates, not Bank Rate. Rob’s report explains how fixed-rate mortgages are funded and why swap rates play such an important role.

“We know not everyone has time to read a detailed technical paper. That is why we have also produced a five-minute guide. Together, the two publications give advisers the information they need to explain these issues with confidence.”

Both publications can be downloaded free of charge from the IMLA website.