Your personal credit file and your business credit file are separate records, but they are often read together. For a sole trader or partnership there is effectively no separation at all. For a limited company, directors are frequently credit searched alongside the business, especially where it is small or newly formed.
Your personal history does not directly change the score an agency calculates for the company. What it does change is how a lender interprets that score, because directors’ conduct is treated as evidence about how the business will be run.
The link tightens where you give a personal guarantee, use personal borrowing to fund the business, or apply for finance in your own name for business use.
Keeping business and personal finances properly separated, with a business bank account and clean records, helps both files be judged on their own merits. It does not remove personal credit from the assessment.