Credit scores affect mortgage rates (the difference between excellent and poor credit can be 0.5-1% on rate), insurance pricing, and even some employment screening. Annual check costs nothing through legitimate services and catches errors.
How to check free
ClearScore, Credit Karma, Experian, Equifax all offer free score and report checks. Once per year minimum. Look for: incorrect information, accounts you don't recognise, late payment markers that don't match your records.
Most adults have at least one error on their credit report. Correcting them is free; the impact on score can be substantial. Five minutes annually pays back over years of better rates.