Every CV you send off should be tailored to each role you apply for. If you’re sending out lots of applications, it can be easy to lose track of which version of your CV you sent where - but this is something you should stay on top of.
If you get invited to an interview, you’ll need a copy of the CV you sent off to hand to help you prepare or to even take to the interview, so you’ll need a system in place to help you find the right one. Similarly, if you get a call from a recruitment agency, you’ll be able to identify how they got your CV in the first place.
When you apply for a specific role, you could create separate folders on your computer for each job application. In this folder, you can include a copy of the job specification, your cover letter and CV, and any other supporting documents you sent off.
When sending off your CV speculatively or when sending it off to an agency or job board, you could include a reference in your CV such as ‘ref: M21-04’ which could tell you that the CV was uploaded to Monster in April 2021. You can then keep a list of all your references which you can cross-reference when you need to.