Formations · Registered Agent

The quiet work
behind every
company & contract.

Mainstay handles the filings, registered‑agent service, and annual compliance that keep your business standing — so the legal scaffolding is never the thing in your way.

A steady hand for founders, operators, and counsel.

We started Mainstay because the people forming companies deserve a filer who treats the work like a craft — accurate the first time, returned on a calendar you can plan around, and answered by a person who knows your file.

From a desk in Sioux Falls, our team prepares and files entity documents in all 50 states. We act as registered agent for thousands of LLCs and corporations, forward service of process the day it arrives, and keep our clients on the right side of every annual deadline.

No upsells. No drip campaigns. Just the paperwork, done the way you'd do it if it were yours.

— Method

Read every line.

Each filing is reviewed by a human formations specialist before it leaves the office. State rejections are an internal failure, not a billable revision.

— Tenure

Twelve years on file.

Established 2014. Our oldest registered‑agent clients have been with us since the year we opened. Continuity is the product.

— Reach

Fifty states, one number.

Domestic formation, foreign qualification, and registered‑agent coverage in every state — handled by the same team you onboarded with.

Two services we do uncommonly well — and a deeper bench behind them.

Most clients come to us for formation or registered‑agent service. Once we're on the file, we handle every downstream filing the entity will ever need.

i

LLC & Corporate Formation

Articles of Organization or Incorporation prepared, reviewed, and filed in your state of choice. Operating agreement template, EIN, and digital records book included.

From$249
ii

Registered Agent Service

A real address, a real human, and same‑day forwarding of service of process. Annual report reminders and a private dashboard for every entity you own.

From$129/yr
Also handled in‑house
— 01
Annual Reports

Filed on time, in every state where you operate.

— 02
BOI Reporting

Beneficial ownership filed and amended as required.

— 03
Foreign Qualification

Register an existing entity to do business in a new state.

— 04
Good Standing

Certified copies and certificates pulled on demand.

— 05
EIN & Tax ID

Federal employer identification number obtained directly.

— 06
Amendments

Name changes, address changes, member changes, dissolutions.

— 07
DBAs

Doing‑business‑as registrations at the county or state level.

— 08
Document Retrieval

Pull historical filings from any Secretary of State.

From intake to filed — usually within the week.

Standard turnaround is two to seven business days, depending on state. Expedited and same‑day options are available where supported.

01

Tell us the entity

Fifteen‑question intake. Type, state, members, intended name. We screen the name against the SOS database before anything is drafted.

Day 0
02

We prepare

A formations specialist drafts your articles, operating agreement, and any state‑specific schedules. You review a clean PDF before we file.

Day 1
03

We file

Filed electronically with the Secretary of State. Expedited where the option exists. Receipt and stamped copy returned to your dashboard.

Day 2 — 7
04

We stay on it

Registered‑agent service activates. Annual report calendar populates. We reach out before every deadline, every year.

Ongoing

A real desk, in a real building, answered by a real person.

Email is fastest. We answer from Central Time, Monday through Friday, and respond to most inquiries within four business hours.

Email hello@mainstayfiling.comFor new filings, existing files, and registered‑agent matters.
Office 3916 N Potsdam Avenue, Suite 1736
Sioux Falls, SD 57104By appointment. Mail and service of process accepted at this address.
Hours Monday — Friday, 8:00 AM — 6:00 PM CTClosed on federal holidays. After‑hours service of process is logged and forwarded the next business morning.
Existing clients Sign in to the dashboard →View entities, download stamped filings, and track upcoming annual reports.
Frequent questions
  • Cheapest state to form?Wyoming, $100
  • Fastest to form?Delaware, <24 hrs
  • Required by every state?Registered agent
  • Annual report due?Varies — we track it
  • Switch agents from elsewhere?Yes, free of charge
Intake

Tell us what you're filing. We'll take it from there.

A formations specialist will reply within four business hours with a quote, a timeline, and the questions we'll need answered to draft your documents.

  • Reply windowWithin 4 business hours
  • Discovery callOptional, 20 min
  • No upfront paymentUntil quote is approved
Form M—01
We'll never share your information. One inbound email per inquiry — no marketing list.