Whilst a verbal contract is just as enforceable as a written one, it's obviously easier to prove the terms of a written agreement. However, it's equally important to make sure that the terms of that contract properly reflect the relationship between the two entities and that you are contracting with the correct entity.
We hate boring you with "legal stuff" but a case in the High Court in 2017 Erith Holdings Ltd and Others v Ronald William Murphy  EWHC 1364 (TCC) highlighted the importance of knowing who you are contracting with and of recording the terms of your agreement formally in writing rather than relying on oral discussions.
When entering into a written contract, double check the legal entities, usually found at the beginning of the agreement. Check the limited company name, company number (really useful, particularly when companies change names or registered office addresses) and registered address or if an individual/sole trader, make sure you have their full name and correspondence address.
Be care of company structures that involve multiple businesses/company names. Make sure you are confident the right one is on the agreement.
Or you could ask your friendly solicitor to run a few simple checks for you, and maybe take a look over the agreement to make sure it properly protects you and reflects the agreement between you and your customer or supplier.
If in doubt, just ask. Better to be safe than sorry! :)