I'm a CPA and managing partner at a commercial real estate firm, so while I don't manage multiple brokerage accounts personally, I deal with complex multi-entity financial tracking constantly. The forensic accounting work we did on that Baltimore shopping center taught me something directly applicable to your question. When we reconstructed missing revenue records across different accounts after a seller expropriated funds, I learned that timing documentation is everything. I created a simple rule: any transaction that might appear in multiple places gets a physical paper trail the day it happens, with handwritten dates I can prove later. For your wash-sale issue, I'd maintain a basic paper log (not just digital) of every sale across all accounts with the 30-day window circled in red pen--sounds old school, but my accountant training says auditable documentation beats clever software every time. The tactic that actually worked: I review everything on the 15th of the month, not at month-end when I'm rushed. That two-week buffer means I catch problems while I still have time to fix them. In December specifically, I do this review on the 10th instead because year-end gets chaotic. Those five extra days have saved me more headaches than any sophisticated tracking system ever did.
I'll be honest--my world is men's health clinic operations and patient care, not investment portfolios. But running CMH-RI across multiple payment systems (insurance claims, cash pay, partner pharmacy accounts) taught me one critical lesson about cross-account reconciliation that maps directly to your question. This past December, I nearly double-counted a medication reorder because we process some prescriptions through Wells Pharmacy Network in Jacksonville and others through our Besse relationship in Pennsylvania. I started flagging any similar transaction within 35 days in our practice management system with a bright red tag and a mandatory second-eye review before year-end books closed. That buffer prevented us from tax headaches when our accountant reconciled everything in January. The tactic that saved us: I keep one master Google Sheet where every significant transaction from every account gets logged the same day with the source and a unique ID number. When December rolls around, I sort by amount and date to catch anything that looks like it could create a reporting problem. Takes me maybe 20 minutes but has caught three potential issues over two years. For actual securities and wash-sale IRS rules, you definitely want a tax pro who lives in that world daily--I'd be guessing beyond my scope. But the discipline of single-source tracking with a 30+ day visual buffer? That's universal across any multi-account situation.