What law covers a false claim of non-receipt of goods through postal service.?

In what context specifically?

That is fraud, but it is not mail fraud. Mail fraud involves getting things posted through the mail without paying postage, for instance... anything that hurts the mail system. Lying about receiving something in the mail that was ordered from a company does not hurt the mail system...- UNLESS, this person had purchased mail insurance and files a claim through the mail system trying to get reimbursed. So if it doesn't directly involve the mail system it isn't mail fraud, it is just simply "fraud".

That would be mail fraud.

As luck would have it, the penalties for committing mail fraud are pretty nasty. Up to 20 years in prison nasty. Fines too. I've included a link to the relevant law.

Mail Fraud.

It is called fraud, and will be covered under those statutes in your state.

That would be "fraud" kid.