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@Newchodge has said you DO have a contract in law whether or not anything has been written down. You agreed to supply products/services and the customer agreed to pay the price. But the reason why it is most unwise to not have a proper written set of terms and conditions is to avoid disagreement as to precisely what has been agreed.
When selling to another country in B2B it is vital to have a jurisdiction clause agreeing that not only that disputes shall be decided in accordance with the laws of England and Wales but that court proceedings can only be issued in the courts of England or Wales. Otherwise the buyer might be able to sue you in his own country. BTW, he usually can in B2C.
Another absolutely vital clause with B2B is to agree that no proceedings will be issued in court until the parties had tried to resolve through mediation. In fact court could be avoided altogether in favour of arbitration (quicker and less costly). I include for clients a very detailed process to be followed by each party including exchanging detailed explanations of position , even before mediation to help reach an agreed resolution.
Another useful clause is one that severely restricts the amount of damages that a buyer is allowed to claim. Again only in B2B.
In fact because your exposure to claims is lower in B2B than with B2C, its often useful to have a clause stating quite clearly that the contract is B2B i.e. that the buyer agrees that when buying he is acting for business purposes. Very useful, for example, when an expensive camera is being bought by a professional photographer which the buyer could, however, claim was for non-business purposes (i.e. a hobby). Obviously laptops would come within this category.
Having a set of terms and conditions may not be a total solution since, subject to website navigation and content, the buyer might be able to argue that he did not read them let alone agree to them.
I could go on as to why it is very unwise not to go to the length of having a detailed and tailored contract (not unadjusted template) especially with your B2B customers. But I guess everyone seems agin me on that.