I've always encouraged clients to send referrals our way - and it works, I've been referral-only for the past two years. When an existing client sends us a new client we gift the existing client 10% of the new clients first invoice [up to $1,000]
And yes, we do offer specials based on anniversaries, etc. but it's usually an 'extra' - a gift to the client - rather than a 'buy X additional hours, rec'v X% off' - but that's certainly something you could do.
Also, when we have a new service to offer and we'd like to market it to our existing clients we'll send out a special offer relative to whatever it is, to help pique interest and introduce the new service.
[Happy one year anniversary! That's a great milestone to have achieved. You should be proud!!

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