The criteria for self-catering accommodation being liable for business rates instead of council tax will change from April 2023.

Currently, properties that are available to let for at least 140 days, and that are actually let for at least 70 days, will pay rates rather than council tax. The change will increase these thresholds to being available to let for at least 252 days and actually let for at least 182 days in any 12-month period.

The change is intended to provide a clearer demonstration that the properties concerned are being let regularly as part of genuine holiday accommodation businesses making a substantial contribution to the local economy.

https://gov.wales/new-tax-rules-second-homes