Nonrecurring (adjective)

Not happening or occurring repeatedly or regularly.

Origin:

Late 19th century: non- + recurring.

Examples:

1. The nonrecurring expense of replacing the roof was not budgeted for.
2. The nonrecurring event of the solar eclipse was a once in a lifetime opportunity.
3. The nonrecurring payment for the software license was a significant cost.
4. The nonrecurring income from the inheritance was a welcome surprise.
5. The nonrecurring budget surplus was a result of careful financial planning.