1
One process
Once your strategy is set, Daysium gives you and the people supporting you one secure process for counting days and keeping the record — instead of relying on spreadsheets, calendars and memory.
For individuals
Know where you stand, before anyone asks.
You have the strategy. Daysium keeps your day counts current against the rules set for your position, and builds the record behind them.
After the advice:
The strategy is clear. The process isn’t.
No proper process
You’re told to keep records. In practice, that means spreadsheets, calendars and memory — a method you have to invent and maintain yourself.
Counting isn’t simple
Residence rules can turn on midnights, transit days, work days, ties and rolling periods. Simply logging where you were is not enough.
A spreadsheet isn’t evidence
It can show what you entered, but not prove where you were. If your position is examined, the supporting record may need to be rebuilt years later.
Why it matters now
Tax authorities have moved on. Your records should too.
Tax authorities are sharing more information across borders, and enquiries can reach years into the past. By then, the question is not what you intended, but what the record can show.
171 million accounts
Financial-account information worth nearly €13 trillion was automatically exchanged across 116 jurisdictions in 2024.
Digital scrutiny
HMRC guidance permits public social media, including Instagram, to be used where proportionate when checking an individual’s tax position, while its use of AI and data science continues to expand.
40 months
HMRC investigations of wealthy individuals yielding more than £100,000 took an average of 40 months to close in 2023–24.
Against that, spreadsheets, calendars and memory
are not much of a system.
Your strategy, put into practice.
Counted, evidenced, defensible.
2
Complex rules, counted for you
Rules automatically apply the logic that changes how days count — midnights, rolling periods, minimums, maximums and declared day types — so you don’t have to calculate it yourself.
3
Proof built as you go
Daysium builds the evidence behind the count as you travel — locations, notes and supporting evidence captured at the time, with changes preserved in the audit trail.
You and your advisors set the strategy.
Daysium keeps the position ready to stand up to scrutiny.
Inside Daysium
One platform. Two parts.
Daysium Mobile counts and evidences your days. Daysium Portal
gives the people you trust a shared view of your position.
Daysium Mobile keeps your day counts current against the rules set for your strategy, builds your timeline automatically as you travel, and lets you add notes and evidence to the record as you go.
Your timeline builds automatically from general locations and places of interest. Add evidence or notes, hide locations, and make constrained corrections preserved in the audit trail. Some day types depend on facts only you know. You declare those yourself.
Send a report from Daysium Mobile when you need a snapshot: where you were, how each day was treated under the rules set for your position, and the count for the period.
Daysium Mobile is what you carry; Daysium Portal is the shared view for the people you trust. They see your position and day counts, not your detailed locations or evidence. You control access.
How we build rules
Every Rule Card starts with the law.
Our assurance process turns tax law into tested, signed-off rules, reviewed and kept current.
Once your strategy is set, Daysium automatically works out the count for you — so you don’t have to interpret the law or calculate it yourself.
Built with the people who use it
Guided by
tax experts
Daysium was shaped with tax advisors, accountants, tax lawyers and former tax inspectors who deal with residence questions and enquiries in practice.
Their experience informs how Daysium counts days, keeps the record and helps make your position easier to evidence when questions arise.
Valuable Partnerships
A pioneering company in the field of day counting and record-keeping. Their innovative tool simplifies complex date-related calculations, offering immense value to our clients. This partnership marks a significant step towards enhancing our client services with advanced solutions.
Alan Kennedy,Managing Director,Trident Tax
Fantastic product
We found out about Daysium from our advisors, it’s a fantastic product, very easy to use and with someone on the end of the phone in case of need or to fix any issues, we would and have recommended it to anyone that would need such a product, it’s totally intuitive too!
Nick T,Monaco No more spreadsheets
After more than two decades of manually counting days spent in various jurisdictions using Excel, I discovered Daysium. It’s transformed how I record my whereabouts — automated, precise, a defensible record ready for when I need it.
Sanjeev P,Zurich Exciting technology
The technology that Daysium has developed is incredibly exciting and I’ve really been enjoying getting under the hood of what’s in store for individuals that utilise the software! The team's passion and vision for solving the ongoing nightmare of tracking for residency status is brilliantly evident.
Rhys Thomas,Managing Director,WTT Group
Founding partners
Frequently asked questions
How does Daysium count my days?
Daysium Mobile uses your phone’s location to build the factual timeline behind the count. If no new location data is available, Daysium records an assumed day based on the previous known location rather than leaving a silent gap. Assumptions and later corrections remain visible. The count is then worked out against the rules set for your position.
Can I use Daysium across multiple jurisdictions?
Yes. Daysium records your travel across borders, and rules can be configured for the jurisdictions relevant to the strategy you are working to. The number included in your membership ranges from one at Professional to our library of jurisdictions at Family Office.
How do you know the residence rules are right?
Each Rule Card is built from identified legal sources and reviewed before it goes live. The source, review and sign-off process is recorded, and the legal sources are re-checked as rules change. How we build rules explains the assurance method in full.
What happens if my position is ever questioned?
You have a dated record built through the year rather than a story assembled only after the event. That record can include location-derived days, visible assumptions and corrections, and supporting evidence you added along the way. Daysium provides the factual record; it does not guarantee a tax or enquiry outcome. Professional advisors are already using Daysium records for clients involved in live tax enquiries.
Does Daysium replace my tax advisor?
No. Daysium provides the day counts, factual record and evidence. Which tax tests apply, what they mean for your position and what you should do remain matters for you and your advisor.
How secure is my data?
Your Daysium data is encrypted and hosted on Google Cloud Platform in the United Kingdom. Daysium is Cyber Essentials certified, with information security controls mapped to ISO 27001:2022 and working towards certification. Access is permission-based and location data is never sold. See Security for the full due-diligence detail.
Recognised by
Finalist two years running at theDigital Jersey TechAwards2024 – Startup Category2025 – Fintech, Startup
#2 Most Recommended StartupOut of 3,000+ companies, Daysium was ranked 2ndin a live, AI-powered scoring of Europe’s topstartups by global VCs & investors
Book a call
In essence
There's nothing to see here — everything is in order.
A life lived across borders, with the record already there when it matters.