The most common mistake we find happens when first starting off is that a Gopher user will set up a customer with a monthly contract fee and then will also charge the customer per scheduled cut. That will cause the customer to be billed twice. They are being charged per cut and then a flat rate at the end of the month. In order to solve this, if you use the contract feature and charge the customer a flat rate each month, set the scheduled job fee to $0.00. Try this and see if it helps.
Turf Pro, are you generating at the end of the month? or at different times throughout the month? Ultimately if you want to send your bills out at the end of the month, only generate at the end of the month. You can ungenerate invoices and then regenerate them if you need to. Go to the invoice page and then right click on the invoice you want to ungenerate then left click on the menu that appears. Then you can generate your invoices again which will combine all your line items into one invoice. If you need more help, please let us know.