The top-ranked teams in each league automatically qualify for the cup. The number of teams accepted into the cup ranges from 128 to a maximum of 32,768. This means that there will always be low-ranked teams in all leagues that aren't allowed into the cup. For example, in a league with 680 teams, 512 will play in the cup. In a league with 10,920 teams, 8,192 will play in the cup. Matches are played mid-week, instead of friendlies. Check the league dates in your league for exact times (these can be found under Upcoming Activities on the main League page).
The first round always takes place the week before the first league game of the season. The first round opponents are announced one week before the games. Opponents for the next round are always determined immediately after the games.
The higher-ranked team always plays away. In the semi-finals and finals, the game is played at a neutral ground
The highest-ranked teams are always seeded to meet the lowest-ranked teams. The team rankings are based on the league positions at the end of the previous season. This means that the ranking stays the same for the duration of the cup.
The home side gets two-thirds of the crowd revenue and the away side gets one-third. This applies to all cup matches except the semi-finals and final when the teams split the revenue 50/50. It's also true that the fans of a Division IV team will want to see a game against a higher division side, but that is not true the other way around. In general, the fans aren't very interested in the first couple of rounds of the cup, but as it goes on, attendance will increase. This means that a Division IV team going far in the cup can make a lot of money!
On top of this, there is also prize money up for grabs, although the big money is made through attendance.
All cup games not settled during normal time go to extra time, and if that doesn't settle the game, there's a penalty shoot-out. During extra time, stamina becomes more important than it was during the second half of normal time and teams lacking experience become even more likely to succumb to nervousness.
If this doesn't end things, then you have to face a nerve wracking penalty shoot-out at the end the game. At every penalty (not during regular match time, though) a test of the players experience is carried out. At this point, don't send forth your shaky 17-year old debutante as the first penalty taker! The skills taken into consideration include scoring ability, set piece ability, as well as the technical specialty for penalty-takers, and the keeper skill for keepers.
You'll find your cup matches under the "Leagues and Cups" link on the left hand side menu. From the Cup page you can check how many rounds have been played, and also see the games played for each round. The early rounds of a cup, however, are not displayed, because there are too many games played.
Remember that your players may get injured during cup matches. As in real life, playing a whole season will take its toll on the squad. Sometimes it might be a better idea to save your best players and play it cool by fielding the reserves. However, the cup is a good opportunity to make yourself some extra money, especially for ambitious teams in Divisions IV and lower. The rewards for participating definitely outweigh the risks, and there's also the matter of the glory. Every year, the best Hattrick players (the winner of the highest league and the cup final winner) get their names engraved in the "Hall of Fame". The cup is also a good opportunity for you to let your players get some valuable match experience, earning about double as much experience as a league match.