A provisional patent application is not examined by USPTO and will not result in a patent. In order to gain the benefit of the provisional application, a non-provisional application must be filed within one year of the filing date of the provisional application and must claim priority to the provisional application. But what if you fail to file the non provisional application within one year of the provisional filing date? Is all benefit of the provisional application lost? Maybe not.
The law provides a two month window after the one year deadline where the benefit of the provisional application can be restored. 35 USC 119(e), 37 CFR 1.78(b), MPEP 211.01(a)(II). But there are important limitations on the option to restore the benefit of the provisional application.
The first limitation is that the delay in filing the nonprovisional application beyond the one year deadline must be unintentional. Therefore if you intended not to file by the one year deadline but then later changed your mind, the delay was probably not unintentional.
The second limitation is that you must file a petition requesting that the benefit of the provision application be restored and pay a big fee.
Currently the fee for this petition is $850 for micro entities and small entities. The petition fee is in addition to the other USPTO filing fees. Generally the USPTO filing fees for a non-provisional application are about $400 for micro entities and $740 for small entities.
Therefore, filing within the two month window where the benefit can be restored effectively more than triples the total USPTO fees to file the application for a micro entity and more than doubles the total fees to file for a small entity.