Reckon and Recon are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It suggests what word you may want to save time, but quite often, its suggestions couldn’t be more off base and produces humorous results.
Reckon is American rural slang. When someone reckons, they are reasoning, drawing a conclusion, or expressing an opinion. To “reckon with” means to anticipate or have to confront obstacles.
The noun form, reckoning, means a climactic, possibly karmic or final judgement type confrontation. In accounting, reckoning means a settling of accounts or final computation.
Recon is an abbreviation for “reconnaissance,” which is a noun. Reconnaissance is an examination or survey used to gather information.
The following story uses both words correctly:
After flying over drought stricken areas on a reconnaissance mission, Reichan reckoned that many families would lose their farms without outside assistance. This wasn’t their first bad season, and they couldn’t afford to stay in business without income. Their day of reckoning would come sooner, not later.