Damian is wearing a red, knit, collarless shirt and denim jacket at 14:24 on the DVD when speaking with St. Clare of Assisi in his cardboard hideaway. After the sports bag of money lands through his roof, he scrambles out in a yellow, knit, collared, school shirt and cloth or nylon jacket.
During the house-building sequence at the beginning of the film, the Moon is seen rising behind the house, but it moves upwards to the left. As the film is set in England (in the northern hemisphere), it should rise towards the right.
Nations transitioning to the euro were allowed to keep legacy currency in circulation as legal tender for two months - and, even after the official dates, they continued to be accepted for exchange by national central banks for varying periods - and indefinitely in some countries.
Though the film is set around the Christmas holiday, several shots show verdant foliage only likely to be seen in summer. Director Danny Boyle explains the season difference at 30:44 in the DVD commentary and says he was told it looks more like Umbria (the Green Heart of Italy) than Manchester.
The film is set around Christmas in England. Yet shadows are relatively short indicating the time of shooting to be summer. The pupils in the playground are not wearing warm clothing, which they would if it were winter.
The goof item below may give away important plot points.
When they are covering the bedroom wall with pounds at 01:17:29 on the DVD, Dorothy is wearing one of Mum's dresses (disclosed as such in "Duffel and Wallpaper" in the deleted scenes of the DVD). However, the same dress is also used as a curtain for Damian's cardboard fort (shown when "the man" is examining it at 29:20 on the DVD).