Microsoft 365 Certified Solutions

Microsoft Office Add-in Development

Microsoft-certified Office.js add-ins for Excel, Outlook, Word, and Teams. Most projects ship in 2 to 8 weeks, for enterprise teams worldwide.

250+Projects Delivered
5+Years Experience
MicrosoftPartner Network
98%Client Satisfaction

Trusted by finance, legal, healthcare & logistics teams worldwide

Microsoft Office Add-in Development
Excel Add-in Development
Word Add-in Development
Outlook Add-in Development
PowerPoint Add-in Development
Power Automate Add-in Development

Trusted by teams across industries

1 Platform
Primmo
EyeMail Inc
Interject
Inflo
MyGatePass
Otisco
Partfiniti
QuikTurn
Tallemu
1 Platform
Primmo
EyeMail Inc
Interject
Inflo
MyGatePass
Otisco
Partfiniti
QuikTurn
Tallemu

What We Do

Custom Microsoft Office Add-ins using Office.js for Excel, Outlook, Word, PowerPoint, SharePoint, and Teams. Delivered in 2 to 8 weeks for enterprise clients worldwide.

Microsoft Office Add-ins Development

Microsoft Office Add-ins Development

MSOfficeAddin builds custom Microsoft Office add-ins for Excel, Outlook, Word, PowerPoint, SharePoint, and Teams using Office.js and the Microsoft 365 platform. From CRM-integrated Outlook add-in workflows to financial-automation Excel tools, our certified developers deliver AppSource-ready, cross-platform solutions for enterprise teams across the US, UK, and Australia.

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Office Add-in Integration Services

Office Add-in Integration Services

Connect your Office add-ins to SAP, Salesforce, Power BI, AI models, REST APIs, and enterprise systems. We build the integration layer so your data flows where your team already works.

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Authentication & Identity

Authentication & Identity

We build the authentication layer for Office add-ins, including Microsoft SSO, OAuth 2.0, Azure AD app registration, and multi-tenant identity. Your users sign in once and the add-in handles everything else.

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AppSource Publishing Services

AppSource Publishing Services

We provide end-to-end Microsoft AppSource submission and certification support, from manifest preparation through reviewer communication and resubmission. We publish your Office add-in to the Microsoft marketplace so enterprise IT admins can deploy it across their organization.

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Excel Add-ins Development

Excel Add-ins Development

MSOfficeAddin specializes in excel add-in development using Office.js, React, and TypeScript, building production-grade Excel extensions, data analysis tools in Excel, and automation add-ins for enterprise teams worldwide. From custom excel ribbon customization that puts your most-used business logic one click away, to API-connected task panes that pull live figures from your ERP without leaving the spreadsheet, every solution is cross-platform, AppSource-certified, and built to scale.

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Outlook Add-ins Development

Outlook Add-ins Development

MSOfficeAddin builds custom outlook add-ins using Office.js, React, and TypeScript, from crm for outlook integrations that sync every customer interaction directly from the inbox, to email automation workflows and calendar add-ins that connect Microsoft 365 to your business systems. Whether you need a CRM connector, a support ticketing tool, a Teams-bridging solution, or a cross-platform enterprise deployment, we scope, build, and AppSource-certify it.

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Why Choose Us

250+ Office Add-in projects delivered since 2021. 98% client satisfaction. AppSource-certified publisher. Microsoft Partner Network member. Office.js and Azure specialists with 5+ years of Microsoft 365 development experience.

250+Projects Delivered
98%Client Satisfaction
5+Years Experience
PartnerMicrosoft Network

Fast Delivery

Simple task-pane add-ins ship in 2–3 weeks. Complex Graph-integrated solutions ship in 6–10 weeks. Every project includes a delivery milestone schedule.

Enterprise Security

Azure AD / Microsoft Entra ID SSO, MSAL.js On-Behalf-Of (OBO) flow, and Microsoft Graph security scopes implemented on every enterprise project.

Expert Team

Office.js specialists with 5+ years building AppSource-certified add-ins. We have completed 50+ VSTO-to-Office.js migrations for enterprise clients.

Technologies We Master

Office.jsReactTypeScriptAzureMS GraphApps ScriptNode.js

What Our Clients Say

Join 100+ businesses who trust us with their critical Office automation and enterprise add-in development.

"Amazing work. The Excel plugin was built exactly around what I needed and has made the process much faster and easier to manage. Communication was clear throughout, the turnaround was quick, and the final result worked well without needing constant back and forth. They clearly understood the problem."

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Chris SimonUnited StatesExcel Add-in Development

"MSOfficeAddin truly exceeded expectations in software development, showcasing impeccable professionalism and profound code expertise. Working with the team was a breeze thanks to excellent cooperation and punctual delivery. HIGHLY recommend their services!"

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Visup SRLRepeat Client · ItalyOffice Add-in Development

"MSOfficeAddin delivered a flawless software project with incredible attention to detail and professionalism. Working with the team was a breeze as they were consistently responsive and cooperative, all while demonstrating EXCELLENT language fluency. 👍"

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Visup SRLRepeat Client · ItalyCustom Add-in Development

"MSOfficeAddin is a true professional team that understands its craft. Very much enjoyed working with them. Even when my schedule got in the way, they accommodated it and were understanding."

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Matt GersbachAustraliaOffice Add-in Development

"I had the pleasure of working with MSOfficeAddin, and I can confidently say that their expertise has been exceptional. They took the time to truly understand our needs, ensuring that the solutions provided were tailored and effective. Communication throughout the process was clear, timely, and always professional."

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Techpreneur MRUMauritiusCustom Add-in Solutions

"An experienced and professional developer. Thank you for the good work!"

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WebzollnerRepeat Client · GermanyOffice Add-in Development

"Great to work with, took time to understand requirements, and delivered to timetable!"

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Graham ClarkRepeat Client · United KingdomOffice Add-in Development

"MSOfficeAddin helped me solve our pain and did it very fast and easy. We're working with them to further enhance and improve our business."

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Casper SankoRepeat Client · DenmarkBusiness Automation Add-in

"Amazing seller, and amazing developer. Great communication to ensure all requests were met, and project was completed as specified. MSOfficeAddin went above and beyond, and worked long hours to complete this project. This was a great experience."

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Revlis01CanadaCustom Add-in Development

"Great communication, delivered ahead of schedule and helped with questions I had. Will contact again for other projects, thank you!!!"

J
Jose MartinezUnited StatesOffice Add-in Development

"You will be happy with the MSOfficeAddin team's services. They did an amazing job understanding user requirements and executing them effectively."

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Abdul HakimUnited StatesOffice Add-in Development

"Perfect work as always. Great experience!"

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Michael ThiemeGermanyOffice Add-in Development

"The MSOfficeAddin team did an outstanding job developing our plugin. They understood our requirements perfectly, communicated clearly, and delivered high-quality results on time. Highly recommended!"

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Nabi UllahSwitzerlandCustom Plugin Development

"Delivered exactly what we agreed on. The tool is working perfectly fine."

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Christoph KutzGermanyOffice Add-in Development

"Delivery within time, clean and well-commented code, extra adjustments, and full deployment on my server. Very professional work and excellent communication."

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Marjolein MosNetherlandsAdd-in Development & Deployment

"If you're looking for someone to help you achieve what you need — the MSOfficeAddin team are the Add-in experts! They developed a fully functional add-in and successfully implemented it in my M365 business account, allowing me to interact with the entire Office Suite and automate as much as possible. I'm very satisfied with their work and will contact them again in the future for sure."

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RobertoRepeat Client · SpainM365 Automation Add-in

"The MSOfficeAddin team has been incredible and provided excellent work on the first delivery."

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Hamid ShafiUnited KingdomOffice Add-in Development

"Exceptional experience working with this developer. Their coding expertise greatly contributed to the project's success."

D
DirkGermanyOffice Add-in Development

"It was a pleasure working with the MSOfficeAddin team. They completed the work quickly and demonstrated strong expertise in Office Add-ins and Microsoft APIs."

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Danish AliAustraliaOffice Add-in Development

"The MSOfficeAddin team understood our requirements for the Outlook plugin we needed. Even with the time zone differences they were able to talk and work around our schedule. Would definitely recommend and use their services again in the future."

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GoMax SolutionsRepeat Client · CanadaOutlook Add-in Development

How we build for Microsoft 365

A structured, compliant, and performance-focused development lifecycle aligned with Microsoft AppSource standards.

STEP 01

Planning & Analysis

Gathering stakeholder requirements and defining scope against Office JS API capabilities.

STEP 02

Architectural Design

Designing Task Pane interfaces using Fluent UI components for a native Microsoft experience.

STEP 03

Development

Iterative coding of manifests and web logic with real-time Office sideloading tests.

STEP 04

QA & Security

Rigorous bug identification and validation against Microsoft security standards.

STEP 05

Deployment

Global rollout via AppSource or centralized tenant deployment via M365 Admin Center.

STEP 06

Maintenance

Ongoing monitoring and compatibility updates for new Microsoft 365 releases.

Frequently asked questions

How do I hire Microsoft developers for custom Office plugins?
Contact us at info@msofficeaddin.com or via the /contact page. We are a Microsoft Partner Network member with 250+ Office Add-in projects delivered over 5+ years. Project quotes are returned within 24 business hours. Engagements start from $3,000 USD.
What is the difference between an Office Add-in and a COM Add-in?
Office Add-ins use HTML, CSS, and JavaScript via the Office.js API. They run cross-platform on Windows, macOS, and Outlook on the Web with no local installation required. COM Add-ins are legacy .NET/Windows-only extensions requiring administrator rights and do not run on Mac or Web. Microsoft has deprecated COM add-in development in favour of Office.js.
Next Steps

Modernize your enterprise with custom Office solutions.

Work with certified Microsoft developers to bridge the gap between your unique data and the tools your team uses every day.

Why start now?

  • Reduce manual data entry by up to 80%
  • Deploy secure SSO-ready add-ins
  • Azure-backed infrastructure

Contact us

Have a project in mind? We're here to help.

Talk to us

Email

info@msofficeaddin.com

Response within 24 hours

Consultation

Book a technical discovery call

Global Support

Working with clients across North America, Europe, and Asia.