We use 911 Pet Chips because they come preregistered to our shelter. They cost about $8.30 per chip and never charge the adopter for registering or making changes - no monthly subscription either. Use the promo code "nonprofit" to receive this price.
I use a Goggle spreadsheet to enter the chip #, animal name, shelter number, adopter name, phone #, address, date of adoption and cat or dog. It can be easily sorted into numerical order for easy reference.
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