We bought a puppy in March 2017, she just completed training (2018) and is now my Service Dog. Can we deduct her purchasing price, vet bills and training,from last year?

[rjs]

Any expenses for the service dog that you paid in 2017 have to be deducted on your 2017 tax return. You cannot deduct them on your 2018 tax return, even if the training wasn't completed until 2018.

If it will make a significant difference in your 2017 tax, you can file an amended return for 2017 to claim the expenses that you omitted. However, the costs for a service animal are deductible as medical expenses. Only total medical expenses in excess of 7.5% of your AGI (for 2017 or 2018) can be deducted. Furthermore, medical expenses are an itemized deduction. If you have any amount to deduct after subtracting 7.5% of your AGI, it will not make any difference in your tax unless your total itemized deductions are more than your standard deduction.