Spokesman Ulrich Pohlmann declined to say when Kohl, 78, would wed his 43-year-old fiance.
But German tabloid daily Bild said Kohl has "already informed his family and close friends of his plans" and would tie the knot "as soon as possible."
The daily said Kohl was still recovering from severe injuries sustained when he fell at his house in the western city of Ludwigshafen in February.
Kohl met Richter, who works for the German economy ministry, four years after his wife Hannelore committed suicide in 2001.
He was chancellor from 1982 to 1998.