Scotland and Wales’ Nations League promotion hopes go to the final day but England cannot progress.
Northern Ireland’s survival bid may depend on a Uefa decision.
Winning your group in the top division sends you to the finals next October, while finishing top of a group in a lower league secures promotion.
The two highest-ranking group winners not to secure a spot for the 2022 World Cup or play-offs through regular qualifying will earn a play-off place.
Finishing bottom of a group in the top two leagues means relegation (League C has relegation play-offs).
So what do the home nations need in the final round of games – and what has already been decided?
Group A2
England: Iceland h (Wed, 18 Nov – 19:45)
England’s game against relegated Iceland on Wednesday is a dead rubber.
Sunday’s 2-0 defeat by Belgium ended Gareth Southgate’s side’s chances of progression to next year’s finals.
They will finish third no matter the result because of their inferior head-to-head record with Denmark.
The winner of Belgium v Denmark qualifies for the finals, with a draw enough for the hosts.
Group B1
Northern Ireland: Romania home (Wednesday, 18 November – 19:45 GMT)
Northern Ireland’s survival hopes are out of their hands after their 2-1 defeat by Austria on Sunday.
They will overtake Romania if they beat them in Wednesday’s meeting at Windsor Park.
But Uefa has to make a decision on what will happen after Norway were unable to play Romania on Sunday because of Covid restrictions. If Romania are awarded one or three points, then NI will be relegated.
Group B2
Scotland: Israel away (Wednesday, 18 November – 19:45 GMT)
Scotland will win promotion to the top flight and boost their chances of a World Cup play-off if they beat Israel on Wednesday.
They could have already sealed promotion had they beaten Slovakia on Sunday, but they lost 1-0.
Steve Clarke’s side can even lose and finish top if the Czech Republic fail to beat Slovakia. The Scots have the head-to-head edge with the Czechs if they finish level on points.
Group B4
Wales: Finland home (Wednesday, 18 November – 19:45 GMT)
Wales – who beat the Republic of Ireland 1-0 on Sunday – will be promoted to League A if they do not lose to Finland on Wednesday.
A win would give them a huge chance of earning a World Cup play-off place because they would have the highest points total of any team in League B.
The Republic of Ireland will be relegated if they lose to Bulgaria.
What has already been decided?
Qualified for next year’s finals: France (A3)
Promoted: Nobody
Relegated: Iceland (A2), Bosnia-Herzegovina (A3)
Relegation play-off: Estonia (C2)
What are some other things up for grabs?
In Group A1, Italy, the Netherlands and Poland are battling it out for a place in the finals – separated by two points with one game to go. Italy just need to beat relegated Bosnia and Herzegovina on Wednesday.
The winners of that group will host next year’s finals.
The winner of Spain v Germany in Group A4 on Tuesday will go to the finals. A draw would be enough for Germany.
The Faroe Islands and Gibraltar only need one point each to move up to the third tier.