--204.210.xxx.xxx

I would think that if you do cash accounting, you would attribute expense to 2018, if accrual, 2017. --67.186.xxx.xxx

Do you have the receipts? If I had the receipts dated 2017 I would add it this year. If not, then his receipt is dated 2018. I generally don't worry about small stuff like that because the likelihood that anyone is going to check on you is small. And really, either way seems to have some common sense to it. --73.33.xxx.xxx

I agree with RichE. If you are cash accounting it would be a 2018 expense. --72.47.xx.xx

Another vote for RichE's answer. --73.102.xxx.xx

I agree, 2018. --76.0.xxx.xx

If you have been filing as cash then yes it is 2018. If you use accrual as I do then it is 2017. It isn't so much a matter of audits as it is a question of taxes. If you are on accrual you are paying taxes on income without the benefit of the applicable deductions. So it really depends on the amount of the expenses. --71.75.xx.xx

Typically it's the date the bill was paid. So what Rich said. --173.170.xxx.xxx

Unless it's on a credit card. Because you don't pay by invoice if you use a CC (unless it's a Home Depot card, for instance.) So if you charge on a CC you expense when it gets charged to the card, right? --50.82.xxx.xx

Yes with credit cards they are expensed on the day of the purchase regardless if you are using cash or accrual. --71.75.xx.xx

if on accrual method you can accrue expenses if incurred in the period regardless of when paid by you. --104.218.xxx.xx