There are two ways it spellchecks. First is auto correct... Which can correct wrong sometimes.
The second is if you notice a word underlined in red tap it once to get suggested replacements. Sometimes it won't show up until you close the keyboard (lower right under shift key).
Check you Settings > General > Keyboard to see what is on or not.
On this forum don't forget you have an edit button and can edit you post at any time.
hi,
ive noticed that the spell check seems to be a bit random :/ ie it doesnt always spot errors - especially where a space has been missed accidently and a letter pressed in its place so that 2 words are joined