Discount for leaving a review

As a web developer, I can tell you that's a huge no-no in Google's terms of use (assuming you are talking about Google Reviews). You risk losing your entire Google listing and all the SEO fu you may have built up. I would suggest that you tread carefully.

https://www.reviewtrackers.com/blog/google-review-policy/

Also, it looks like it would be an FTC violation.

https://www.ftc.gov/business-guidance/resources/featuring-online-customer-reviews-guide-platforms

@wendell this is great info to have.  Thank you!  We’re meeting with our website guy tomorrow, I’ll get these read thoroughly and discuss with him some of of our other options.  Appreciate your time replying.

@absurveyor18548 No problem! Happy to help keep you out of hot water.

Don't give them a discount.

Give them a voucher - one that they can pass to their friends.

Odds on, you'll never see it claimed anyway.

But it does engender the "warm fuzzies" on behalf of the client (and their family)

My 2 cents:

Coupons are used to buy groceries, sales or discounts are used to buy cars and clothes.  Neither should apply to Professional services.  We provide a service not a widget.

Again, just my 2 cents.

I tihnk Maryland would frown upon that based on this from the Code of Ethics in COMAR. 

.06 Improper Solicitation of Professional Employment.
A. Other than the usual commissions paid to licensed employment agencies, a licensee may not compensate, give anything of value, or offer to compensate or give anything of value, as follows:

(1) To a person or organization to recommend or secure the licensee’s employment as a professional land surveyor or a property line surveyor; or

(2) As a reward for having made a recommendation resulting in the licensee’s employment as a professional land surveyor or a property line surveyor.

B. When competing for professional employment, a licensee may not falsify or permit misrepresentation of the licensee’s qualifications or those of the licensee' associates.

C. An employed licensee may not solicit or accept other employment to the detriment of the licensee’s regular work or the interests of the licensee’s employer.