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Accounting · head to head

IRIS KashFlow vs Polar

IRIS KashFlow logo

IRIS KashFlow

Accounting

Online accounting software for UK sole traders and small businesses

From
£13.5/month
Rated
-
Full reviewWebsite
Polar logo

Polar

Accounting

Billing and revenue platform for AI and infrastructure companies

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Polar has a free tier, so it costs nothing to try first.
  • Each has a real cost: IRIS KashFlow advertised monthly prices of £1.35 (Starter) and £2.75 (Business) are a 90% promotional discount off the standard £13.50 and £27.50 rates, and the promotion is described as lasting 6 months before reverting; Polar percentage-based fees higher than some specialized processors for high-volume transactions
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which IRIS KashFlow and Polar actually diverge.

Attributes where IRIS KashFlow and Polar differ
AttributeIRIS KashFlowPolar
Starting price£13.5/monthFree
Pricing modelsubscriptionPercentage of transaction plus per-transaction fee
Free tierNoYes
PlatformsWebWeb, API

Identical on both: user rating (Not yet rated), category (Accounting).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in IRIS KashFlow

Nothing recorded that Polar does not also cover.

Only in Polar

  • Usage Billing
  • Subscriptions
  • Seat Management
  • Prepaid Credits
  • Hosted Checkout
  • Cost Insights
  • Merchant of Record

What people use each for

The jobs each tool is most often brought in to do.

IRIS KashFlow

  • business accountingnot Polar
  • invoicing and billingnot Polar
  • VAT managementnot Polar

Polar

  • Billing for token and API call consumption by LLM applicationsnot IRIS KashFlow
  • Managing tiered pricing for infrastructure usage-based servicesnot IRIS KashFlow
  • Handling subscription and usage hybrid modelsnot IRIS KashFlow
  • Monetizing AI APIs with usage metering and creditsnot IRIS KashFlow

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

IRIS KashFlow

  • Advertised monthly prices of £1.35 (Starter) and £2.75 (Business) are a 90% promotional discount off the standard £13.50 and £27.50 rates, and the promotion is described as lasting 6 months before reverting
  • Listed prices are in GBP plus VAT, and the platform's plans are built around UK VAT filing rather than other tax regimes
  • Annual pricing is quoted at RRP £162/year (Starter) and £291.50/year (Business) before the same promotional reduction

Polar

  • Percentage-based fees higher than some specialized processors for high-volume transactions
  • Merchant of record model may not suit companies preferring direct payment control
  • Free Starter tier limited with 5% fees reducing appeal for production use
  • Setup and integration effort required despite API simplicity

Pricing, plan by plan

IRIS KashFlow

£13.5/month
  • Starter Monthly$13.5/month
    • 10 invoices
    • up to 25 bank transactions
    • single user access
  • Business Monthly$27.5/month
    • unlimited invoices
    • unlimited bank transactions
    • multi-user access
  • Starter Annual$162/year
    • 10 invoices
    • up to 25 bank transactions
    • single user access
  • Business Annual$291.5/year
    • unlimited invoices
    • unlimited bank transactions
    • multi-user access

Polar

Free
  • StarterFree
    • 5% + $0.50 per transaction
    • Free tier for testing
    • Basic features
  • Pro$20/month
    • 3.8% + $0.40 per transaction
    • Full platform access
    • Cost insights
  • Growth$100/month
    • 3.6% + $0.35 per transaction
    • Priority support
    • Volume benefits
  • Scale$400/month
    • 3.4% + $0.30 per transaction
    • Dedicated support
    • Custom integration

Which should you pick?

Choose IRIS KashFlow if

Nothing in the data separates IRIS KashFlow from Polar on the points above - pick on price and on how each one feels to use.

IRIS KashFlow review

Choose Polar if

  • You need usage billing.
  • You want to start without paying.
  • You work on Web, API.
  • You also want subscriptions.
Polar review

Questions people ask

Is IRIS KashFlow or Polar better?
Neither clearly leads. IRIS KashFlow starts at £13.5/month and Polar at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, IRIS KashFlow or Polar?
Polar has a free tier; the other does not. Paid plans start at £13.5/month for IRIS KashFlow and Free for Polar.
Does IRIS KashFlow or Polar run on more platforms?
IRIS KashFlow runs on Web. Polar runs on Web, API.
Can I use Polar for free?
Yes. Polar has a free tier, so you can try it without paying. IRIS KashFlow starts at £13.5/month.
What is IRIS KashFlow best used for?
IRIS KashFlow is most often used for business accounting, invoicing and billing, vat management. Of those, business accounting and invoicing and billing are not what Polar is typically brought in for.
What can IRIS KashFlow do that Polar cannot?
Polar covers Usage Billing, Subscriptions, Seat Management, Prepaid Credits.

Answered from the vendors’ own pages

IRIS KashFlow: What are IRIS KashFlow's core features across all plans?

All IRIS KashFlow plans include unlimited quotes, online VAT submission, mobile app access, 50+ reports, bank feeds, receipt capture, multi-currency support, and payroll for up to 5 employees.

Source
Polar: Do you handle international payments and taxes?

Yes, Polar acts as merchant of record in 100+ markets, handling payment processing, tax collection, and compliance automatically.

Source
IRIS KashFlow: Are there promotional discounts for new IRIS KashFlow customers?

Yes, new customers receive a 90% discount for 6 months on both Starter and Business monthly plans.

Source
Polar: Is there a free tier?

Yes, the Starter plan is free and charges 5% + $0.50 per transaction, ideal for testing and early-stage development.

Source
IRIS KashFlow: Can multiple users access IRIS KashFlow on the Starter plan?

No, the Starter plan is limited to single-user access only. Multi-user access requires the Business plan.

Source
Polar: Do you offer discounts for startups?

Yes, the Startup Program provides the Scale plan free for 12 months for early-stage AI companies.

Source
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