The decision against Kroon, 24, is reportedly the toughest handed out to an equestrian in the federation's history.
Two of her horses, Gucci and Rolex, were found to have been treated with pain relieving substances four days before the HFRK Grand Prix, in Helsingborg in February.
The horses were treated with the prescription drugs flunixin and Adequanin. One horse was treated with both. Flunixin is a non-steroidal anti-inflammatory drug (NSAID) with analgesic and anti-rheumatic properties. Adequan is a glucosamine based product which stimulates cartilage repair and reverses traumatic joint dysfunction, according to the manufacturer. Both are on the Swedish Federation's list of banned substances.
"This is an important decision, and it is a clear message from the Disciplinary Board," said Swedish Equestrian Federation President Bo Helander.
"It is always our job to protect the welfare of the horse," he said.
The preparations used on the two horses required a 14-day stand-down before competition. The Swedish Equestrian Federation was made aware of the situation and then made a complaint to the Disciplinary Board. Under the rules of the Swedish federation, it is not a requirement that there is a positive test for determining a violation of the rules. However, the regulations state that facts surrounding a case "may be established by any reliable means", the disciplinary board said at Kroon's hearing.
"It is therefore important that Sofia Kroon stated she did not know that Adequanin / Adequan was classified as an unauthorized substance, or that she was not aware of exactly where Rolex was injected into the knee joint, or that she did not have information about withholding times," the disciplinary board said.
"Instead, it was her responsibility to investigate these issues before she competed Rolex and Gucci in Helsingborg," the board said.
Kroon has appealed but the outcome is not expected until next month.
Kroon has been a successful rider for the Swedish equestrian team, with wins in both pony and junior international events. She has not been competing since the case came to light, but has been coaching young riders for international competition.