Can I claim expenses before the business is open?

Can I file for expenses for my new business before the end of the year, but open and register my new business after the new year? I already bought  , printer,computer and alike, but haven't  register or opened my new business and plan to do it after the new year of 2018.  Will I lose them if won't open business before 2018? 

Will they carry to the next year is my business will be registered only in 2018, or I'll lose those expenses?

Can I claim those expenses in 2017, even though my new business is not opened or registeted yet?

Thank you.