Can I lump 15-20 invoices into one letter for a single general contractor

I'm the material supplier to one sub-contractor who installs our product for one general contractor. I got a bad feeling about one of our clients, and have verified all the invoices from February in the system. It's one customer with over 3 dozen invoices, but only 3 General Contractors. Can I lump the multiple invoices to each of the three respective general contractors ? These are for new home sales, and I'm not sure if someone even purchased this homes in the past 2 months - should I just blanket send each invoice to each of the homes as well ?