A COA that only lists nicotine strength and nothing else is a red flag. A proper report should cover the analytes that matter for your market—heavy metals, carbonyls, and sometimes residual solvents or microbials. If you're selling in the US, you should know what the FDA expects for your product category. In the EU, the TPD has its own list.

Also, check the method. The report should say whether they used HPLC, GC-MS, or something else. If it doesn't, ask. A lab that's vague about methods isn't worth your trust.