This year, tax reform could give U.S. companies access to hundreds of billions of dollars they have stashed overseas. Many corporations can't wait that long.

Apple Inc. and Microsoft Corp. sold a total of $27 billion of debt this week to fund their daily operations, repay maturing debt and buy back shares. Those bond sales might be unnecessary if new tax laws come this year because under President Donald Trump's proposed plan, companies could pay a one-time 10% levy to bring back money held overseas, less than a third of the current rate.

Apple CEO Tim Cook told investors this week that he was “confident” that “some sort of tax reform” would be coming this year. But until it goes into effect, borrowing is still the best bet for many companies, said Jordan Chalfin, an analyst at debt research firm CreditSights.