He maintained he paid his taxes.

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. He maintained he’s innocent of failing to pay his taxes.
  2. He was found innocent of conspiring to kill the king.
    Are these sentences correct?
2

He maintained he’s’ is a mix of tenses. (he’s = he is)
He maintains he is…
He maintained he was…
Other than that, ‘innocent of failing to pay his taxes’ is an odd phrase. It would not be voiced in that way.

3

It would be more usual to say: He was found not guilty of failing/failure to …

4

That changes the sense though, as there is no indication in the original sentence that he has been found not guilty.

I think to maintain the sense a more usual saying would be: He maintained that he did not fail to pay his taxes.

5

How about: He maintained he paid his taxes.[YSaerTTEW443543]

TOEIC listening, photographs: Sitting around a table[YSaerTTEW443543]

6

That’s the most straightforward option. I’m trying to stay as close as reasonable to the original and assumed that there was a focus i=on the failure within the original accusation.