Hi, a local client is owing me money against my...

Although your question is not clear, here is the following information:
If you have a contract that defines the rights and duties of both the seller and the buyer, you can file a lawsuit against the person who refuses to pay the value of your products that he received and did not pay you for.
You have to present to the judge a copy of the contract in addition to any document proving that the buyer has received your products
And if you have other evidence such as a receipt for the products, you can also file a lawsuit against the buyer in order to request the value of your products in addition to compensation for the damage you suffered because of
Not paying for your products.