RentalBux vs. IRIS KashFlow
Which MTD Software Is Better for UK Landlords?
Overall Winner: RentalBux
RentalBux is the more complete MTD software for UK landlords and sole traders. It combines full Making Tax Digital compliance across UK property income, foreign property income, and self-employment income with comprehensive property management, automated bookkeeping, AI-driven expense categorisation, joint ownership profit-splitting, and a free plan for single-property landlords until March 2028. IRIS KashFlow is a cloud-based accounting platform first released in 2005 and now owned by IRIS Software Group. It is HMRC-recognised for MTD ITSA and offers a comprehensive accounting toolkit including VAT returns, CIS, multi-currency, and optional payroll. However, IRIS KashFlow is not purpose-built for landlords — it has no property portfolio management, no tenant management, no joint ownership profit-splitting, no HMO-specific features, and no free plan. Recent Trustpilot reviews (1.5 stars, 160+ reviews) raise significant concerns about customer service and platform reliability that landlords should carefully consider before committing.
At-a-Glance MTD Software Comparison
Key differences between RentalBux and IRIS KashFlow across MTD compliance, property management, bookkeeping, pricing, and landlord-specific features.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Software Type | Property/Landlord Platform | |
| Target Users | Landlords, Sole Traders, Letting Agents | |
| Income Sources Supported | Sole Trader + UK Property + Foreign Property | Sole Trader + UK Property (foreign property not confirmed for MTD ITSA) |
| Free MTD Software Plan | Free until March 2028 (1 property) | No free plan (14-day free trial only) |
| MTD Quarterly Updates to HMRC | Yes | Yes |
| Final Declaration | Yes | Yes |
| Bank Reconciliation | Yes | Yes |
| Automated Bank Feeds | Yes | Yes |
| Invoice Creation | Yes | Yes |
| Receipt Capture (OCR) | Yes | Yes |
| Expense Auto-Categorisation | Coming soon | Yes |
| Property Portfolio Management | Yes | No |
| Tenant Management | Yes | No |
| Joint Ownership & Profit Sharing | Yes | No |
| Payroll | No | Yes |
| HMO Unit-Level Tracking | Yes | No |
| HMRC SA105 Box Pre-Mapping | Yes | No |
| Spreadsheet Import/Export | Yes | Yes |
| Platform | Web, iOS, Android | Web, iOS, Android |
| GDPR Compliant | Yes | Yes |
| Software type | General Small Business Accounting Software | |
| Target users | Sole Traders, Contractors, SMEs, Limited Companies |
What Is RentalBux? What Is IRIS KashFlow?
What Is RentalBux?
All-in-One MTD Software for Landlords and Sole Traders
RentalBux is an all-in-one property management, accounting, and Making Tax Digital compliance platform built specifically for UK landlords, letting agents, and self-employed individuals. Designed with direct input from accountants who specialise in property and sole trader tax, RentalBux covers everything from tenancy management and rent collection to full bookkeeping with a pre-configured chart of accounts tailored to the property sector.
RentalBux is fully HMRC-recognised for Making Tax Digital for Income Tax across all three qualifying income categories: UK property income, foreign property income, and self-employment. This makes it one of the only landlord-specific MTD software platforms that can handle a landlord who also runs a sole trader business, all from a single subscription.
A major differentiator is RentalBux's pricing model: single-property landlords can use the platform completely free until March 2028, making it one of the most affordable HMRC-approved MTD software options for landlords entering the MTD regime.
What Is IRIS KashFlow?
Online Accounting Software Made Simple
IRIS KashFlow is a cloud-based accounting platform first released in 2005 and acquired by IRIS Software Group in 2013. IRIS is the UK's largest private sector provider of business-critical software, with over 100,000 business customers across the country. KashFlow is one of IRIS Group's bookkeeping tools, positioned within a broader IRIS ecosystem that includes IRIS Elements, IRIS Accountancy Suite, and KashFlow Payroll.
IRIS KashFlow serves sole traders, contractors, small businesses, growing businesses, and limited companies. All plans include VAT returns with direct HMRC submission, bank feeds, receipt capture, mobile access, and a customisable dashboard with 50+ reports. The Business plan adds multi-user access, unlimited invoicing, unlimited bank reconciliation, and multi-currency. The Business + Payroll plan adds payroll for up to five employees via integration with IRIS Payroll. KashFlow Connect (Orbit) is IRIS KashFlow's accountant portal, allowing practices to manage multiple client accounts and support MTD ITSA submissions.
Strengths
- Free MTD software for single-property landlords until March 2028
- Handles sole trader + UK property + foreign property income in one platform
- Joint ownership with automatic profit-sharing split by ownership percentage
- Pre-built chart of accounts tailored for landlords and sole traders
- AI-powered expense auto-categorisation and OCR receipt capture
- Agent filing on behalf of landlords — ideal for accountants and letting agents
- Supports HMO properties with auto-created units
Strengths
- HMRC-recognised for MTD ITSA (landlords and sole traders)
- Full VAT returns with direct HMRC submission on all plans
- CIS support for construction subcontractors
- Multi-currency on Business plan
- Optional payroll (up to 5 employees) on Business + Payroll plan
- Open Banking bank feeds on all plans
- KashFlow Connect (Orbit) accountant portal — supports agent filing
- Integrations with Zapier, Stripe, PayPal, GoCardless
- 90% off for 6 months for new customers; 14-day free trial
Limitations
- Newer to market compared to established platforms
- No yield or LTV investment analysis tools
- No MTD for VAT support yet
- Some advanced reporting features still in development
- Limited third-party app integrations
- No offline capability
- No tax liability forecasting feature currently
Limitations
- No free plan — paid-only from £12.50/month + VAT
- Trustpilot rating of ~1.5 stars from 160+ reviews — significant concerns about reliability and customer service
- No property portfolio management, tenant management, or HMO features
- No joint ownership or automatic profit-splitting
- No confirmed foreign property income support for MTD ITSA
- Starter plan limited to single user and 10 invoices/month
- Payroll only on top-tier Business + Payroll plan (£34/month + VAT)
- KashFlow Trustpilot page not actively monitored by IRIS
- Recent reviews cite data deletion, billing issues, and poor support responsiveness
Making Tax Digital Compliance
How RentalBux Handles MTD Compliance
RentalBux supports all three MTD qualifying income categories: sole trader income, UK property income, and foreign property income. This makes it suitable for landlords who also earn self-employment income, eliminating the need for separate software. Most accounts are pre-mapped to HMRC Self-Assessment boxes. RentalBux also supports agent filing, allowing accountants or letting agents to submit MTD returns on behalf of their landlord clients.
How IRIS KashFlow Handles MTD Compliance
IRIS KashFlow is HMRC-recognised for MTD ITSA and applies to unincorporated sole traders and landlords with qualifying income above £50,000. IRIS has committed to delivering an end-to-end MTD ITSA solution within KashFlow including quarterly update submissions, customisable periodic update reports, tax calculations, and submission reminder emails and logs. Agent filing is supported via the KashFlow Connect (Orbit) accountant portal, which allows practices to manage client MTD submissions. IRIS KashFlow is part of the wider IRIS Group MTD offering, which also covers IRIS Elements, IRIS Elements Cashbook, and the IRIS Accountancy Suite.
IRIS KashFlow's official documentation confirms support for "unincorporated / sole trader businesses and landlords" for MTD ITSA purposes. However, foreign property income support specifically within KashFlow's MTD ITSA workflow is not clearly confirmed in KashFlow's official landlord-facing documentation — landlords with overseas rental income should verify this directly with IRIS before committing.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| HMRC Recognised (MTD ITSA) | Yes | |
| MTD Quarterly Updates | Yes | Yes |
| Final Declaration | Yes | Yes |
| Digital Record Keeping | Yes | Yes |
| Digital Links Compliant | Yes | Yes |
| Sole Trader Income | Yes | Yes |
| UK Property Income | Yes | Yes |
| Foreign Property Income | Yes | Not confirmed |
| Multiple Income Streams | Yes | Yes |
| Agent Filing on Behalf | Yes | Yes |
| HMRC Recognised (MTD VAT) | Yes |
Winner: RentalBux for landlord-specific MTD compliance. Both are HMRC-recognised and support MTD quarterly updates and agent filing. RentalBux's confirmed foreign property income support, automatic joint ownership handling, and purpose-built property workflow give it a clearer advantage for landlords. IRIS KashFlow leads for landlords who also need VAT returns, CIS, or payroll on the same platform.
Property Management
RentalBux: Property Management
RentalBux provides comprehensive property portfolio management with tenant management, rent tracking, property expense allocation, and support for multiple properties. A standout feature is its joint ownership and profit-sharing capability: landlords can define ownership percentages once, and RentalBux automatically splits rental income and expenses. RentalBux also supports HMO properties, automatically creating individual units.
IRIS KashFlow: General Accounting — No Property Management Features
IRIS KashFlow does not include property-specific management features. There is no built-in property portfolio management, tenant management, rent tracking, HMO support, or joint ownership profit-splitting. IRIS KashFlow can be used to track rental income and property expenses through its general bookkeeping tools — income can be recorded, expenses categorised, and bank transactions reconciled — but all property categorisation and organisation must be done manually within a general-purpose framework. Landlords with multiple properties would need to manually manage per-property tracking within KashFlow's general ledger structure.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Property Portfolio Management | Yes | No |
| Tenant Management | Yes | No |
| Rent Tracking | Yes | Manual (general income tracking) |
| Property Expense Allocation | Yes | Manual (general income tracking) |
| Multiple Property Support | Yes | Manual setup only |
| HMO Property Support | Yes (auto-creates units) | No |
| Joint Ownership/Profit Sharing | Yes (auto-split by %) | No |
| Maintenance Tracking | No | No |
| Tenant Screening | No | No |
| Compliance Document Alerts | Yes | No |
| Arrears Tracking | No | No |
Winner: RentalBux — IRIS KashFlow has no built-in property management features. RentalBux's purpose-built property toolkit — including tenant management, HMO auto-unit creation, and joint ownership profit-splitting — is unmatched for landlords.
Bookkeeping, Accounting & Digital Record Keeping
RentalBux: Structured Accounting
RentalBux includes a pre-built chart of accounts specifically designed for landlords and sole traders, covering rental income, mortgage interest, insurance, property repairs, professional services, utilities, and tenant deposits. All accounts are pre-mapped to HMRC Self-Assessment boxes. The platform supports cash basis accounting, bank reconciliation, and journal entries.
IRIS KashFlow: Established General Business Accounting with VAT, CIS, and Payroll
IRIS KashFlow provides a comprehensive accounting toolkit for small businesses: double-entry bookkeeping, bank reconciliation via automated Open Banking feeds, a customisable general chart of accounts, VAT returns with direct HMRC submission on all plans, CIS support, multi-currency on the Business plan, and optional payroll via IRIS Payroll on the Business + Payroll plan. Its 50+ reports include P&L, balance sheet, cashflow, and aged debtors. Receipt capture (KashFlow Quick Capture) is available on all plans. The Starter plan is limited to a single user and 10 invoices per month — a meaningful constraint for busy landlords. The Business plan removes these limits and adds multi-user access.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Cash Basis Accounting | Yes | Yes |
| Chart of Accounts (Pre-built, Landlord-Tailored) | Yes (pre-built + custom) | Yes (general) |
| Journal Entries | Yes | Yes |
| Bank Reconciliation | Yes | Yes |
| Automated Bank Feeds | Yes (Major UK banks) | Yes |
| Open Banking Integration | Yes | Yes |
| Double-Entry Bookkeeping | Yes | Yes |
| HMRC Box Pre-Mapping | Yes | No |
| Xero Integration | No | No |
| Spreadsheet Import/Export | Yes | Yes |
| Digital Record Storage | Yes | Yes |
Winner: Depends on use case. RentalBux wins for landlord-specific bookkeeping structure with no setup required. IRIS KashFlow wins for breadth — VAT, CIS, payroll, purchase orders, multi-currency, and mileage tracking make it a more complete business accounting tool for landlords with wider commercial activities.
Invoicing, Expense Tracking
RentalBux: Expense Management
RentalBux includes OCR receipt capture, structured expense tracking with landlord-specific categories, auto-categorisation, invoice creation with customisable branding, and payment tracking with reminders.
IRIS KashFlow: Receipt Capture and Business Invoicing
IRIS KashFlow includes KashFlow Quick Capture for receipt capture on all plans, allowing receipts to be photographed and stored. VAT is automatically updated and submitted directly to HMRC. Invoice creation is highly customisable with branded templates and automatic reminder emails. Recurring invoices are available on the Business plan. The Starter plan limits invoices to 10 per month and bank reconciliation to 25 transactions — constraints that may be insufficient for landlords with active portfolios. The Business plan removes all limits. Some users have noted in reviews that the mobile app's receipt handling is less seamless than desktop, requiring upload via Dropbox rather than direct capture in some cases.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Invoice Creation & Sending | Yes | Yes |
| Invoice Customisation/Branding | Yes | Yes |
| Online Payment Collection | Yes | Yes |
| Payment Tracking/Reminders | Yes | Yes |
| Expense Tracking | Yes | Yes |
| Receipt Capture (OCR/Photo) | Yes | Yes |
| Expense Categorisation | Yes | Yes |
| Automated Transaction Matching | Yes | Yes |
| Mileage Tracking | No | Yes |
| AI Auto-Categorisation | Coming soon | No |
Winner: RentalBux for landlord expense management. AI-powered OCR receipt capture is available on all RentalBux plans including free, with landlord-specific expense categories. IRIS KashFlow's Quick Capture works on all plans but has reported mobile limitations, and expense categories are general business rather than landlord-specific.
Reporting & Tax Forecasting
RentalBux: Formal Accounting Reports
RentalBux produces structured financial reports including profit & loss statements, balance sheets, journal reports, ledger reports, and trial balances. Smart categorisation helps ensure accuracy.
IRIS KashFlow: Comprehensive Business Reporting with 50+ Reports
IRIS KashFlow provides a full suite of 50+ financial reports including P&L, balance sheet, cashflow, aged debtors, aged creditors, VAT reports, and customisable management reports. The dashboard is fully customisable to display the metrics most relevant to the business. Tax calculations are included within the MTD ITSA workflow. IRIS KashFlow does not provide a standalone running tax estimate feature separate from the MTD submission workflow.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Profit & Loss Report | Yes (formal) | |
| Balance Sheet | Yes | Yes |
| Trial Balance | Yes | Yes |
| Dashboard/Overview | Yes | |
| Real-Time Financial Data | Yes | Yes |
| Cash Flow Reporting | No | Yes |
| Tax Estimate/Forecast | Yes | No |
| AI-Powered Features | Coming soon | No |
| Profit & Loss | Yes | |
| Dashboard / Overview | Yes |
Winner: IRIS KashFlow on report breadth; RentalBux for property-focused reporting. IRIS KashFlow's cash flow reports, VAT reports, and 50+ customisable report suite give it greater general business reporting depth. RentalBux leads on property-specific reporting within its broader property management context.
Collaboration & Mobile Apps
RentalBux's Collaborative Features
RentalBux enables agent filing, which gives accountants and letting agents the ability to submit directly on a landlord's behalf.
IRIS KashFlow: Free Accountant Portal with Deep IRIS Ecosystem Integration
IRIS KashFlow's accountant portal --- KashFlow Connect --- is free for accountants and bookkeepers with no per-client charge. Accountants can manage multiple KashFlow client accounts from a single dashboard, with real-time access to transactions, reports, and MTD filing status. KashFlow Connect integrates directly with IRIS Accountancy software, used by over 17,000 UK accountancy firms, giving practices a seamless flow from client bookkeeping data to accounts production and tax filing. Agent filing for both MTD VAT and MTD ITSA is fully supported via KashFlow Connect.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Accountant/Advisor Portal | Yes | |
| Multi-User Access | Yes | Business plan only (Starter is single-user) |
| Agent Filing on Behalf | Yes | Yes |
| Bank Integration | Yes | Yes |
| Platform | iOS, Android | iOS, Android |
| Web Browser Access | Yes | Yes |
| FCA Regulated | Yes | No |
| GDPR Compliant | Yes | Yes |
| Accountant / Advisor Portal | Yes |
Winner: Tie on collaboration tools; RentalBux for reliability. Both offer dedicated accountant portals and agent filing. IRIS KashFlow's broader integrations via Zapier and payment providers are a genuine advantage for businesses with existing tech stacks. However, the significant concerns raised in recent reviews about IRIS KashFlow's customer service responsiveness and platform reliability are an important consideration for landlords choosing their primary MTD compliance tool.
Ease of Use, Support & Security
RentalBux: Guided Workflows
RentalBux uses guided workflows, clear dashboards, and no accounting jargon. The platform offers phone support, email/chat support, and a help centre with guides and knowledge base articles.
IRIS KashFlow: Ease of Use
IRIS KashFlow has been designed for small business owners and sole traders without formal accounting training. The cloud-based interface is accessible from any browser or via the mobile app, with a clear sidebar navigation and customisable dashboard. Bank feeds automatically import transactions from major UK banks, and the invoicing workflow --- from quote to payment via IRIS Pay --- is designed to require minimal accounting knowledge. The platform's 20-year history means its core interface is mature and well-documented through the KashFlow Akademy training library and support knowledge base.
| Feature | RentalBux | IRIS KashFlow |
|---|---|---|
| Phone Support | Yes | Limited (see review concerns) |
| Chat Support | Yes | Yes |
| Email Support | Yes | Yes |
| Help Centre/Knowledge Base | Yes | Yes |
| FCA Regulated | Yes | No |
| Enterprise-Grade Security | Yes | Yes |
RentalBux Features
Sole Trader Income Support for MTD
RentalBux is one of the few landlord-focused MTD software platforms that supports self-employment income alongside UK and foreign property income within a single account. Landlords who also run a trade, consultancy, or freelance business can manage all quarterly submissions from one dashboard. Landlord Studio covers property income only.
Custom Chart of Accounts for Landlords
A property-tailored chart of accounts covering rental income, mortgage interest, insurance, repairs, utilities, letting agent fees, and more — all pre-mapped to HMRC Self-Assessment boxes. No setup required; the system is ready to use from day one. Landlord Studio has no equivalent.
Agent Filing on Behalf of Landlords
Letting agents and accountants can submit MTD quarterly updates and the Final Declaration on behalf of landlord clients directly from the platform. Landlord Studio allows accountant access but does not support submission on the landlord's behalf.
Branded Invoice Creation
Invoice creation with customisable branding for service charges and commercial landlords. Not available in Landlord Studio.
AI-Powered OCR Receipt Capture with Auto-Categorisation (Coming soon)
RentalBux's AI will read uploaded receipts and categorise the expense automatically against the pre-built chart of accounts. Landlord Studio's Smart Scan extracts dates and amounts but does not include AI-driven expense categorisation.
Formal Accounting Reports
Balance sheet, trial balance, ledger reports, and journal reports. Landlord Studio does not produce these natively.
Free Plan Including MTD Submissions Until March 2028
RentalBux's free single-property plan includes MTD quarterly submissions. Landlord Studio's free GO plan covers property management for up to three units but requires a paid PRO plan (from £12/month) to access MTD submission functionality.
Unique Features Only IRIS KashFlow Offers
MTD for VAT on All Plans
IRIS KashFlow is fully HMRC-recognised for Making Tax Digital for VAT with direct submission to HMRC on all paid plans. This is essential for VAT-registered landlords and property businesses, and is built into every KashFlow subscription at no extra tier cost.
CIS Support
IRIS KashFlow supports Construction Industry Scheme (CIS) submissions, which is valuable for landlords who carry out property renovation, development, or building work involving subcontractors. CIS handling is confirmed in user reviews as a strength.
CIS (Construction Industry Scheme) Support
IRIS KashFlow includes built-in CIS withholding tax calculations on applicable invoices, CIS deduction recording, and CIS reports --- available on all plans. This makes it suitable for contractors and subcontractors working within the Construction Industry Scheme.
Optional Payroll (Up to 5 Employees)
The Business + Payroll plan (£34/month + VAT) integrates with IRIS Payroll for up to five employees. For landlords who employ property managers, cleaners, or administrative staff, payroll can be managed within the IRIS ecosystem.
Multi-Currency
IRIS KashFlow's Business plan supports multi-currency transactions — useful for landlords invoicing international tenants or managing international financial relationships.
Mileage Tracking
IRIS KashFlow includes mileage tracking on all plans, allowing landlords to claim vehicle expenses for property visits.
Purchase Orders
IRIS KashFlow supports purchase orders for managing supplier transactions — useful for landlords who regularly commission contractors for maintenance and development work.
Zapier and Payment Gateway Integrations
IRIS KashFlow connects to Zapier (enabling automation with Google Sheets, Slack, Trello, and hundreds of other apps), Stripe, PayPal, GoCardless, and IRIS Pay. For landlords with existing tech stacks or e-commerce/payment workflows, these integrations provide meaningful automation capability.
IRIS Group Ecosystem
As part of the IRIS Software Group, KashFlow integrates with IRIS Elements (for accountants), the IRIS Accountancy Suite, KashFlow Connect, and KashFlow Payroll. For practices already within the IRIS ecosystem, KashFlow provides a familiar, integrated environment.
Who Should Choose RentalBux?
RentalBux is a strong fit if you:
Landlords with Mixed Income Streams
If you earn from both property and self-employment, RentalBux handles sole trader income alongside UK and foreign property income in a single MTD-compliant platform.
Joint Owners and Family Portfolios
The automated profit-sharing split is a standout feature. Define ownership percentages once and RentalBux calculates each owner's share automatically.
Budget-Conscious Landlords Entering MTD
Free MTD software for single-property landlords until March 2028, with no upfront commitment.
Landlords Who Want Proper Accounting Structure
Chart of accounts, journal entries, profit & loss, balance sheet, and trial balance give RentalBux a structured accounting foundation.
Accountants and Letting Agents
Agent filing on behalf, multi-user access, and spreadsheet import make RentalBux practical for professionals managing multiple landlord portfolios.
Commercial Landlords and HMO Owners
Invoice creation with branding for service charges, plus automatic HMO unit creation and tenant management.
Who Should Choose IRIS KashFlow?
IRIS KashFlow may be the better choice for:
Landlords Who Are Also VAT-Registered
If your rental portfolio sits alongside a VAT-registered business and you want MTD ITSA and MTD for VAT managed in a single platform at every subscription tier, KashFlow provides this integration natively.
Landlords in Construction or Property Development
CIS support makes KashFlow a practical choice for landlords who carry out renovation, development, or building work with subcontractors. User reviews specifically confirm CIS handling as a strength.
Landlords Already Embedded in the IRIS Ecosystem
If your accountant uses IRIS Elements or the IRIS Accountancy Suite, or you already use KashFlow for your wider business, staying within the IRIS ecosystem may simplify accountant collaboration and software management.
Landlords Who Need Multi-Currency or Purchase Orders
If you invoice international tenants in foreign currencies or regularly commission suppliers using purchase orders, KashFlow's Business plan provides these capabilities.
Landlords Who Want to Use Zapier Automations
If you run a broader business with existing Zapier workflows connecting to Google Sheets, Slack, CRM tools, or e-commerce platforms, KashFlow's Zapier integration enables automation.