The suggestion given by ITS is probably correct, an alternative is "avkastningsbyte" which is used as well. This refers to A) the swap between different commercial papers (with different interest rates) or B) the swap between the yield from commercial papers and the yield from stocks.

However, your context makes me inclined to believe that this refers to a specific, US type of investment fund.
If I'm correct, then the swapping part means something entirely different.

These funds (open only to wealthy private citizens) are aiming to reduce tax for it's owners. In exchange for buying stocks the investor will reduce his/hers capital gains tax.

This is what Times.com wrote about these funds:

"Through something called swap funds, also known as exchange funds, Wall Street has divined a way for some overly concentrated investors to trade one stock that has risen for a basket of stocks of equal value--avoiding any immediate capital-gains tax. A crush of financial firms, including Banker's Trust, Salomon Smith Barney, J.P. Morgan and Donaldson Lufkin Jenrette, are launching swap funds right now."

This type of fund does not have an equivalent in Sweden. If you cannot use the (US) english description, my suggestion above would probably be appropriate.