Your terms of business can only apply in law if you made the client aware of them before accepting the job. (That would have given the potential client the opportunity to either agree to them or to look elsewhere for someone to do the work). You can't simply spring them on him when you submit your invoice.
Similarly, if you've not agreed payment terms in advance with the client, he can't suddenly tell you that his terms give him a year to pay.
The legal position is that, without a prior agreement about payment terms, the client has SIXTY days within which to make his payment to you. So, by making his payment within just 30 days, the client is actually being generous to you.