The biggest issuers of U.S. corporate bonds are easing up on selling new securities, which could translate to gains for investors holding the debt.

Banks and other financial companies have sold around US$50 billion of bonds so far this year, down more than 40 percent from the same period a year ago. For the largest U.S. banks, the decline has been even steeper—they sold just $12 billion of debt after earnings, about a third of sales at the same point last year.

Debt sales are falling after banks have largely sold enough debt to meet the requirements of a Federal Reserve regulation, and tax cuts have lifted their cash flow, reducing their borrowing needs. Many foreign banks, typically major January issuers, have sat out amid Brexit jitters and rising hedging costs in currency markets. U.S. and foreign financial companies represent about a third of the $5 trillion high-grade bond market.