Is a company laptop or cell phone a taxable benefit if I also use it personally?

Generally, no — a company laptop or cell phone that's used primarily for work, with only incidental personal use, is generally not treated as a taxable benefit. Occasional personal calls, texts, or browsing on a device that's fundamentally there for your job doesn't typically trigger the kind of employment-benefit treatment that applies to more clearly personal perks.

The analysis can change, though, if the personal use becomes significant rather than incidental. If a device provided for work ends up being used substantially for personal purposes — functioning more like a personally-provided phone or computer that happens to be paid for by the employer, rather than a work tool with occasional personal use layered on top — that shift in the pattern of use can move the equipment into taxable-benefit territory, or at least raise the question of whether some portion of its value should be treated that way.

Because "incidental" versus "significant" personal use is a matter of degree rather than a bright-line rule, employers providing devices for work should have some reasonable expectation or policy about personal use, and employees should be mindful that treating a company device as their primary personal phone or computer changes the tax picture, even if no one intended that shift to happen.