Get Started With
Castell Tax Experts
Bookkeeping, tax preparation, and business advisory from a family-led team of Enrolled Agents. We work with growing businesses across Nampa, Boise, and the Treasure Valley.
What We Do
Monthly bookkeeping starting at $195. Tax preparation for businesses and individuals. Payroll tax services. Catch-up work for books that are months or years behind. IRS and state tax representation when things get complicated. Pick one service or bring us in for all of it.
Who We Work With
Contractors, restaurants, real estate professionals, manufacturers, farms, professional services, and other growing businesses across the Treasure Valley. If you're building something and need real financial support, we can help.
What Happens Next
Fill out the form and we'll reach out within 24 hours. We'll ask about your business, review your current situation, and give you a clear quote.
Let's Talk. We Respond Within 24 Hours.
50 Years Experience • Team of Enrolled Agents • 200+ Clients
Something went wrong. Please try again or reach us directly at hello@castelltax.com.
We got your message.
Someone from our team will be in touch shortly.
Request a Quote
Tell us about your business. We'll get back to you within 24 hours.
You Can Also Call or Text: (801) 550-2613
What Brought You Here?
The books are behind, tax season caught you flat-footed, or you're wondering if you're paying more than you should.
Tax Season Suprise
Your accountant needs your books and they're not ready. You're scrambling to find receipts and hoping you didn't miss anything important. We get your records in order and make sure you're prepared before the deadline.
An IRS Notice in Your Mailbox
That letter from the IRS is sitting on your desk and you're not sure what to do with it. As Enrolled Agents, we're federally licensed to represent you directly. We handle the response, the calls, and the resolution.
Leaving Money on the Table
You filed your return but you're not confident you claimed everything you could have. Most business owners miss deductions they're entitled to. We review every transaction and identify what others overlook.
The Books Are Months Behind
Every week you tell yourself you'll catch up. Every week you don't. Now it's a pile of statements and transactions you can't make sense of. We dig in, sort it out, and bring you current.
Outgrowing DIY Bookkeeping
QuickBooks made sense when you started. Now it's full of miscategorized transactions and accounts you don't recognize. We clean it up, restructure it properly, and keep it running right going forward.
Starting a Business
LLC or S Corp? How do you set up your books? What about payroll taxes? The early decisions matter. We help you choose the right structure and build your accounting foundation correctly from day one.
Why Work With Us
A family-owned tax and accounting practice with 50+ years of experience and a team of federally licensed Enrolled Agents.
Enrolled Agent Team
Every member of our team is an Enrolled Agent. That's a federal credential that allows us to represent you directly before the IRS. When tax issues get complicated, we handle it ourselves.
50+ Years of Experience
Our founder, Diane Castell, has been in this business for five decades. She started at 18 working alongside her CPA father. That kind of experience means we've seen almost everything.
Local to Treasure Valley
We're based in Nampa and serve businesses across Boise and the Treasure Valley. This is our community. Our reputation is here, and that's a kind of accountability that matters.
Year-Round Partnership
We're not just tax preparers you hear from once a year. We work with you throughout the year to keep your books current, plan ahead, and make decisions that save you money.
Our Services
Small business bookkeeping, tax preparation, and advisory services. From monthly books to IRS representation, we handle it all.
Bookkeeping
Clean, accurate books maintained throughout the year. General ledger management, bank reconciliations, and monthly financial statements. Flat monthly fee with unlimited questions.
Monthly & Quarterly Performance Reporting
Profit and loss statements, balance sheets, and KPIs delivered on a regular schedule. These reports show you what's actually happening in your business so you can make decisions based on facts.
Controller Services
Financial oversight for businesses that need more than basic bookkeeping. We review your books monthly, implement internal controls, and catch problems before they become expensive.
CFO & Advisory Services
Financial strategy and advisory for businesses ready to grow. Budgeting, forecasting, cash flow planning, and the ongoing guidance you need to make confident decisions.
QuickBooks Setup & Training
System design, setup, and conversion from manual or other platforms to QuickBooks. Includes training and ongoing software support.
New Business Setup
Get your accounting system, payroll, and tax structure set up correctly from day one. For startups and first-year businesses ready to build on a solid foundation.
New Business Strategy
LLC, S Corp, or C Corp? We analyze your situation and recommend the entity structure that fits your goals and minimizes your tax burden.
Industry-Specific Accounting & Tax
Accounting built for how your industry actually works. We specialize in construction, restaurants, real estate, manufacturing, and professional services.
Business Tax Preparation
Comprehensive tax preparation and filing for all business entity types. Federal, state, and multi-state returns handled by Enrolled Agents who identify every available deduction and credit.
Personal Tax Preparation
Full-service tax preparation for individuals with investments, rental properties, self-employment income, and other complex situations.
Estate Tax Preparation
Preparation of estate, trust, and gift tax returns. We handle the specialized filings required when wealth transfers between generations and ensure everything stays compliant and tax-efficient.
Sales Tax Compliance
We manage your sales tax obligations from registration through filing. You collect the tax from customers and we handle everything else. Returns are prepared, filed on time, and tracked so nothing slips through the cracks.
Payroll Tax Services
Payroll tax calculation, filing, and compliance. We handle quarterly and annual returns so you stay current with the IRS and Idaho. Deadlines tracked and deposits managed.
Out-of-State Tax Returns
Multi-state tax compliance for businesses operating across state lines. We determine where you have filing obligations and prepare returns for each state where you owe.
IRS Audit Representation (Enrolled Agent)
When the IRS sends a notice or starts an audit, you need someone with federal authority to represent you. As Enrolled Agents, we handle the IRS directly so you don't have to.
State Tax Representation
When Idaho's tax agency sends a notice or starts an audit, you need someone who knows the rules and procedures. We handle state tax issues on your behalf.
Financial Planning for Business Owners
Integrates accounting and tax strategy with long-term financial and retirement planning. Aligns business and personal finances for future success.
Inventory Accounting
Inventory tracking, valuation, and reporting for product-based businesses. We maintain accurate cost of goods sold so you know your real margins.
What Our Clients Say
We've worked with over 200 businesses. Here's what a few of them have to say.
"Diane Castell has been my accountant almost 10 years and she is amazing. I highly recommend her for personal and business tax prep. She is efficient, knowledgeable, and easy to work with. I always walk away feeling confident her work is correct and that I saved way more money in taxes using her than trying to do it on my own. I have moved to different states and continue to count on Diane for my tax prep."
Andrea Zavitz
"Diane is so important to my business. If not for her I would be flailing. Tax preparation for a "C Class" corporation is best done by a highly trained professional, Diane is exactly that. She handles my company's books and is extremely knowledgeable about the current requirements and details needed to file accurate and critical corporate tax returns. She answers all of my questions without hesitation and actually encourages me to ask them. Her work is prompt and punctual. She is a true expert and deeply experienced in her field. I highly recommend her company to any persons or businesses in need of tax related services."
Patrick McIntyre
"I am so grateful for Diane at Castell Tax Experts. She answers all of my questions whenever I want to further understand my tax situation. All forms are filed in a timely manner and the Invoices I receive are clear. Glad to have a professional Enrolled Agent in my corner for all my business and personal needs."
Annneli Castell
Common Questions
Quick answers to things people usually want to know before getting started.
How much does bookkeeping cost?
Monthly bookkeeping starts at $195. Your rate depends on your expense volume and the complexity of your books. We'll review your situation and give you a flat monthly quote before anything starts.
My books are behind. Can you fix them?
Yes. We do catch-up work regularly. We'll look at how far back things go and give you a project quote to get everything current and accurate. Once we're caught up, we move into regular monthly service.
Is there a contract?
No long-term contracts. We work month-to-month. If things change and you need to move on, just give us 30 days notice.
How do I send you documents?
We use a secure portal for document uploads. It's simple to use, and we'll walk you through the setup when you come on board.
Do we need to meet in person?
Not required. We can handle everything remotely. If you're local to the Treasure Valley and prefer to meet face to face, we're happy to do that too.
What accounting software do you support?
We work with QuickBooks Online, QuickBooks Desktop, and QuickBooks Desktop Enterprise. If you're not on QuickBooks yet, we can help you get set up and trained.
What do I need to do each month?
Connect your bank feeds or upload statements and receipts. Maybe 15 minutes of your time. We handle the reconciliation and reporting from there.
Do you handle payroll?
Yes. We manage payroll tax calculation, filing, and compliance. That includes quarterly returns and year-end W-2s.
Do you file taxes?
Yes. We prepare and file business and individual tax returns. Our team includes Enrolled Agents, so we're licensed to handle everything from straightforward returns to complex situations.
What if I get audited?
That's where we really help. As Enrolled Agents, we're federally licensed to represent you directly before the IRS. We handle the communication, respond to notices, and negotiate on your behalf.
How quickly do you respond?
Same day during business hours. If you call or email with a question, you'll hear back before the day is over. We encourage questions.
How soon can you start?
Usually within a few days. If your books need cleanup, we start there first. If everything is current, we jump right into monthly service.
The Treasure Valley's Tax and Accounting Team
The Next Step:
A Short Conversation
Tell us what you're dealing with. We'll listen, answer your questions, and give you a straightforward quote.