Your Numbers. Our Expertise.
You didn't start your business to spend nights buried in spreadsheets or chasing unpaid invoices. We handle the back-office — accounting, payroll, AR, revenue cycle — so you can get back to the work that actually matters.
- Licensed & Insured Professionals
- Local & Nationwide Service
- Dedicated Account Manager
"Every client gets a real person — not a portal, not a call center. I know your business by name, and I pick up the phone."— Rhiannon Mastrella, Founder
What We Do
Comprehensive Business Services
From daily bookkeeping to complex revenue cycle management — we're the back-office partner that keeps your business running smoothly.
Accounting & Bookkeeping
Full-cycle accounting for small and mid-size businesses. Monthly reconciliations, financial statements, and real-time visibility into your books.
- Monthly close & reconciliation
- General ledger management
- Financial statement prep
Accounts Receivable (AR)
We manage your billing, collections, and aging reports so you get paid faster and reduce outstanding balances.
- Invoice generation & tracking
- Collections follow-up
- AR aging analysis
Revenue Cycle Management
End-to-end RCM services to optimize cash flow, reduce denials, and streamline your billing process — especially for service-based businesses.
- Claim submission & tracking
- Denial management
- Payment posting & reporting
Payroll Processing
Accurate, on-time payroll for businesses of all sizes. We handle calculations, compliance, direct deposit, and year-end filings.
- Direct deposit & check processing
- Payroll tax withholding & filings
- W-2 & 1099 preparation
Financial Reporting & Analysis
Clear, easy-to-understand reports that give you confidence in your numbers and insight into your business performance.
- Profit & loss statements
- Cash flow forecasting
- KPI dashboards
Not sure where to start?
Let's figure it out together — for free.
Every engagement starts with a free consultation. Tell us what's keeping you up at night, and we'll tell you exactly how we can help.
Businesses Served
Years of Experience
Client Retention Rate
Nationwide Reach
Why Business Owners Choose Us
We're More Than
an Accounting Firm
Rhiannon Mastrella founded Koios after spending her career inside Fortune 500 healthcare companies — watching small business owners struggle with the exact problems she'd spent years solving for much larger organizations.
You get one consistent point of contact who knows your business and genuinely wants to see it grow — whether you're running one location or operating across multiple states.
Licensed & Credentialed
Every member of our team is a trained, licensed professional.
One Dedicated Contact
No call centers, no runarounds — one person who knows your business.
Local Roots. Nationwide Reach.
Serving clients across all 50 states with local-market understanding.
Bank-Level Security
Enterprise-grade encryption and full industry privacy compliance.
98%
Client retention rate
50
States Served
The Person Behind Koios
Rhiannon Mastrella
Founder & Principal, Koios Business Solutions
15+
Years in Finance
Meet Rhiannon
Mastrella
"I started Koios because I believe every business owner deserves to know exactly where their money is — without having to chase anyone down for answers."
Rhiannon founded Koios Business Solutions after spending her career inside Fortune 500 healthcare companies and watching small business owners struggle with the exact problems she'd spent years solving — late collections, messy books, payroll stress, and financial reports nobody could actually read.
With deep roots in healthcare revenue cycle management, controllership, and financial reporting, she brings institutional-grade expertise to businesses that have never had access to it before. Her clients get a real expert — not a call center, not a portal — someone who knows their business by name and picks up the phone.
Education
B.S. Healthcare Admin (Finance) · A.S. Health IT, Southwest Florida College
Background
Fortune 500 healthcare · Private practice · Controller, William C. Huff Companies
Philosophy
Every client deserves institutional-grade financial clarity — regardless of business size
Getting Started Is Easy
How It Works
From first call to fully supported — most clients are onboarded within one week.
"Onboarded in under a week."
— Marcus T., HVAC Company Owner
Free Consultation
Tell us about your business, current challenges, and goals. No obligation, no hard sell — just a real conversation with an expert.
Custom Proposal
We design a service plan tailored to your specific needs and budget. You'll know exactly what you're getting before anything is signed.
Seamless Onboarding
We connect your systems, migrate your data, and get up to speed on your business — without disrupting your operations.
Ongoing Partnership
Your dedicated account manager keeps your books clean, your payroll on time, and your cash flow healthy — month after month.
Industries We Serve
Built for Business Owners Across Every Sector
Client Stories
What Our Clients Actually Say
Real business owners. Real results. No scripts.
"I was drowning — late payments piling up, payroll stressing me out every two weeks. Koios stepped in and within a month my collections were actually running. I finally feel like I'm in control of my own business again."
Marcus T.
Owner, Regional HVAC Company
AR Collections + Payroll
"I'd tried two other bookkeeping services before and both felt like I was just another account number. With Koios, I have one person who calls me back, knows my practice, and speaks to me like a partner."
Sandra R.
Owner, Dental Practice · 3 Locations
Accounting & Bookkeeping
"They're like having a CFO on call without the full-time salary. Every time I pick up the phone, they already know the context. No re-explaining, no runaround — just answers."
David K.
Founder, Logistics Company
Financial Reporting
Get In Touch
Let's Have a Real
Conversation
No sales pitch. No pressure. Just a straightforward conversation about your business — what's working, what's not, and whether we're the right fit to help.
Your free consultation includes a review of your current setup, honest recommendations, and transparent pricing — so you always know exactly what you're getting.