Sometimes its accidental, using the wrong card linked to say Amazon, and sometimes its because it makes sense, for example with BBX.
For example BBX have a trade show which focuses on personal purchases
If you’re self employed then any personal spending is Drawings.
Drawings don’ affect your tax as you pay tax based on your profit.
The most common treat is to post personal expenses to the directors loan account. This is a balance sheet account and shows the balance the director owes to the company or that the company owes the director.
The Directors Loan Account is often cleared with dividends.
Alternatively the personal expenditure could be treated as additional salary or as a benefit in kind.
You can’t reclaim VAT on personal expenditure.
Whatever you do make sure the Directors Loan isn’t overdrawn 9 months after year end or you will pay an additional temporary tax charge.