Making changes

SOLVED

Hello. I have no accounting training but have recently taken over AR/AP for our company.

I am not sure how the accountant has been closing off each month as balanced given the number of errors I have been finding. In any case, I need help knowing how to make corrections to things in a previously closed period.

Example 1...Power bill for $93.45 from April (which is now closed) finally got paid July 15.

Example 2...Repair invoice for $120 from April 4 was actually paid April 15 but was never recorded as paid.

Example 3...Water bill for $84.75 from April 2 was incorrectly recorded as paid April 15 but did not actually get paid until July 15.

Any help would be appreciated.

EDIT:

The point of my question is how to make changes in a "CLOSED" period. A closed month means I am not allowed to touch it, so I can't just change dates or void previous transactions. Anything I do needs to be done in the current month. So, for the examples I gave:

Example 1...Power bill for $93.45 from April (which is now closed) finally got paid July 15. How do I post the July 15 payment so that it zeros out the $93.45 that is still showing from April without touching April.

Example 2...Repair invoice for $120 from April 4 was actually paid April 15 but was never recorded as paid. How do I record an April 15 payment now and link it back to the April 4 invoice without touching April?

Example 3...Water bill for $84.75 from April 2 was incorrectly recorded as paid April 15 but did not actually get paid until July 15. How do I make this adjustment without touching April?