Solo 401k plans in Control Group question

My husband and I own two companies that both only employ the two of us. We make W-2 salaries out of both. Last year I opened both Roth and traditional solo 401ks and was told I could contribute from both companies up to the total max since the IRS would see this as a Control Group. How does this get reported to the IRS? How do I stay compliant tax wise? Do I just file my taxes normally and report the contributions? Do I need to change the plan documents to show contributions can come from the two businesses even though it was set up for just one?