PatriciaV's answer was for non-business bad debts but you asked about a business bad debt. The answer is probably not, but you should follow IRS Publication 535, Chapter 10. The version for TY 2018 is at https://www.irs.gov/publications/p535#en_US_2018_publink1000154202 Scroll down about 5/8ths of the page to 10. Business Bad Debts. Note that
"You can claim a business bad debt deduction only if the amount owed to you was previously included in gross income. This applies to amounts owed to you from all sources of taxable income, including sales, services, rents, and interest. "
TT H&B 2018 search will find Jump to bad debt, self-employed income which will land you at Business Income and Expenses - Here's the business info we have so far, but it offers no further help 😕
