Yes, you can just put years on your resume; however, we don’t recommend it for your most recent work history.
Leaving the exact months you were employed off your resume’s work experience section can help you avoid including a gap in your work history and make your experience appear more consistent.
If, however, you leave off the months (e.g. you put 2019-2020), expect to be asked exactly how long you worked in a particular role during an interview or screening call. The difference between a possible 23 months (Jan 2019 – Nov 2020) and 2 months (Dec 2019 – Jan 2020) is huge in an employer’s eyes, and if they feel you are lying or trying to stretch the truth, they won’t hire you.
For any professional experience more than 10 years old and the time you completed your education, it is entirely acceptable to include the years with no months on your resume.