Here are several changes that could affect the many small businesses:

1.Qualified Business Income Deduction

Many owners of sole proprietorships, partnerships, trusts and S corporations may deduct 20 percent of their qualified business income.  

2. Temporary 100 percent expensing for certain business assets

Businesses are now able to write off most certain depreciable business assets in the year the business places them in service.  

3.Fringe benefits

• Entertainment and meals: The new law eliminates the deduction for expenses related to entertainment, amusement or recreation.
• Qualified transportation: The new law disallows deductions for expenses associated with transportation fringe benefits or expenses incurred providing transportation for commuting.
  
• Bicycle commuting reimbursements: Employers can deduct qualified bicycle commuting reimbursements as a business expense for 2018 through 2025. Employers must now include these reimbursements in the employee’s wages. 
• Qualified moving expenses reimbursements: Reimbursements an employer pays to an employee in 2018 for qualified moving expenses are subject to federal income tax.
  
• Employee achievement award:  An employer may deduct awards that are tangible personal property, subject to certain deduction limits.

Reference:

https://www.irs.gov/newsroom/irs-several-tax-law-changes-may-affect-bottom-line-of-many-business-owners