YOU SAID:

I will only do this once a year.

INTO JAPANESE

私はこれを1年に1回だけ行います。

BACK INTO ENGLISH

I will do this once a year.

INTO JAPANESE

私はこれを年1回行う予定です。

BACK INTO ENGLISH

I plan to do this once a year.

INTO JAPANESE

私はこれを1年に1回行う予定です。

BACK INTO ENGLISH

I plan to do this once a year.