Are the heirs entitled to claim the income from the shop that the deceased's wife rented, relying on her husband's business license after his death?

Official documentation is not a condition for the validity of a lease. If the lease contract is valid and has a specified term, the death of the tenant does not invalidate the contract. Rather, the right of usufruct transfers to their heirs until the end of the contract term, unless it is terminated by mutual consent or by a judicial ruling. However, if the lease is on a monthly basis (i.e., "for such-and-such amount per month" without specifying a term), either party may terminate the contract at any time. In this case, the heirs do not have the right to join the wife if she concludes a new contract with the landlord.