GSP will renew on April 22, 2018 through 2020.
CBP will begin to process automatic refunds for products that claimed GSP during the lapse since it got expired on 12/31/17 shortly after April 22. Duties will be refunded without interest and go to the importer of record. For the products that did NOT claim GSP during the lapse must request refunds to CBP. According to CBP’s website, these refund requests (post-imporation GSP claims) can be submitted as letters, Post Summary Corrections (PSC) or protests.
The deadline to submit refund requests is September 19, 2018.
Please see the below link for more information.