Tax residency, compliance, and proof of presence — defined.
Every term you need to understand tax residency rules, cross-border compliance, and how certified proof of presence works.
A
-
183-Day rule
The most common threshold for determining tax residency worldwide. If you spend 183 days or more in a country within a defined period (calendar year or rolling 12 months), that country generally considers you a tax resident and may tax your worldwide income.
Learn more -
AES-256
Advanced Encryption Standard with 256-bit key length. Military-grade encryption used by ResidenceSafe to protect all stored data. Considered unbreakable with current computing technology.
B
-
Beckham law (ley Beckham)
Spain's special tax regime (Art. 93 LIRPF) offering a 24% flat tax rate on Spanish-source income for qualifying new residents. Originally designed for transferred workers, expanded in 2023 to include remote workers and entrepreneurs. Requires 183+ days of physical presence.
Learn more -
Biometric verification
The use of unique biological characteristics (facial features, fingerprints) to confirm identity. ResidenceSafe uses liveness detection to ensure the person checking in is physically present, preventing spoofing or proxy check-ins.
-
Blockchain certification
The process of recording a cryptographic hash of data on a distributed, immutable ledger. Each ResidenceSafe check-in is sealed on-chain, creating a tamper-proof record that can be independently verified.
Learn more
C
-
Center of vital interests
A criterion used alongside the 183-day rule to determine tax residency. Considers where your family lives, where your primary business or employment is located, and where your main economic and personal ties are concentrated. Even if you spend fewer than 183 days, this test can establish residency.
-
Certified geolocation
GPS coordinates captured at the moment of a verified check-in, cryptographically sealed and timestamped. Unlike continuous tracking, certified geolocation records a single verified point of presence.
-
Check-in
In ResidenceSafe, a single verified presence record consisting of biometric verification (selfie with liveness detection) combined with certified GPS coordinates. Takes under 30 seconds. Creates one blockchain-sealed record per check-in.
-
CRS (common reporting standard)
An OECD framework for automatic exchange of financial account information between participating countries. Over 100 jurisdictions share banking data, meaning your home country can see your financial activity abroad.
D
-
Digital nomad visa
A residence permit designed for remote workers employed by or contracting with companies outside the issuing country. Available in Spain, Portugal, Croatia, Greece, Estonia, and 40+ other countries. Most require proving minimum income and physical presence.
Learn more -
Double taxation
When two or more countries claim the right to tax the same income. Occurs when residency status is disputed or when tax treaties don't fully resolve conflicting claims. Double Taxation Agreements (DTAs) exist between many countries to mitigate this.
E
-
eIDAS 2
The updated EU regulation on electronic identification and trust services (Regulation 2024/1183). Establishes the legal framework for electronic signatures, seals, and timestamps across EU member states. ResidenceSafe uses eIDAS 2 PAdES LTA signatures for legally recognized document certification.
Learn more -
EES (Entry-Exit system)
The EU's new biometric border control system replacing passport stamps at Schengen external borders. Records entry/exit dates with fingerprints and facial images. Phased rollout from October 2025, full deployment expected April 2026. Tracks Schengen entry/exit but NOT per-country movement within Schengen.
Learn more -
ETIAS (European travel information and authorisation system)
Pre-travel authorization required for visa-exempt non-EU nationals visiting the Schengen Area. Links to EES for border control. Expected to launch alongside EES full deployment.
-
Exit tax
A tax imposed on unrealized capital gains when a taxpayer changes their country of residence. Spain's exit tax (Art. 95 bis LIRPF) applies to residents leaving with unrealized gains exceeding EUR 4 million.
Learn more
G
-
GDPR (general data protection regulation)
EU regulation (2016/679) governing the collection, processing, and storage of personal data. ResidenceSafe is fully GDPR-compliant, with data minimization, purpose limitation, and user control at its core.
-
Golden visa
A residence-by-investment program offering residency permits in exchange for significant financial investment. Available in Portugal (EUR 500K+ fund investment), UAE (AED 2M+ property), Spain (ended 2025), Greece, and others. Residency permits granted do NOT automatically confer tax residency.
-
GPA (GPS position accuracy)
The precision of a GPS coordinate measurement. ResidenceSafe records GPS accuracy metadata with each check-in to validate the reliability of the geolocation data.
-
GPS corroboration
The use of GPS coordinates to corroborate (support) a claim of physical presence. In ResidenceSafe, GPS is a supporting layer alongside biometric verification, not a tracking mechanism.
H
-
Habitual abode
A concept used in tax treaties (OECD Model Convention Art. 4) as a tiebreaker for dual residency. Refers to the country where a person spends more time overall, considering the frequency, duration, and regularity of stays.
I
-
IFICI regime
Portugal's Incentivo Fiscal a Investigacao Cientifica e Inovacao, replacing NHR from January 2025. Offers 20% flat tax for 10 years to qualifying professionals in research, R&D, startups, and innovation sectors.
Learn more -
Immutability certificate
A document proving that a specific record has been sealed on a blockchain and cannot be altered. Each ResidenceSafe check-in generates an immutability certificate with a verification link.
-
ISO 27001
International standard for information security management systems (ISMS). Defines requirements for establishing, implementing, maintaining, and improving an ISMS.
K
-
KYC (know your customer)
Identity verification procedures required by financial institutions and regulated services. ResidenceSafe's biometric verification serves as a form of KYC, confirming the identity of the person checking in.
L
-
Liveness detection
Technology that distinguishes a live person from a photo, video, or mask during biometric verification. ResidenceSafe uses liveness detection to prevent anyone from checking in on your behalf using a photograph.
M
-
Modelo 720
Spain's foreign asset declaration form. Spanish tax residents must declare foreign assets exceeding EUR 50,000 in three categories: accounts, securities, and real estate. Historically carried penalties up to EUR 150,000 (reduced after EU Court ruling 2022). Remains a key audit trigger for emigrants.
N
-
NHR (Non-Habitual resident)
Portugal's former special tax regime (2009-2024) offering favorable rates on foreign income for 10 years. Closed to new applicants January 2025. Replaced by IFICI. Existing NHR beneficiaries retain their status for the full 10-year period.
P
-
PAdES LTA (PDF advanced electronic signatures, Long-Term archival)
A standard for digitally signed PDF documents that remain verifiable long after signing, even after certificates expire. ResidenceSafe uses PAdES LTA format for eIDAS 2 compliant report signatures.
-
Physical presence test
A tax residency test based solely on the number of days physically spent in a country. The 183-day rule is the most common version. Some countries (UK, US) use more complex multi-factor tests.
Learn more -
Private key
A cryptographic key known only to its owner, used to create digital signatures. In blockchain certification, the private key proves authorship and prevents tampering.
-
Proof of presence
Documented evidence that a specific person was physically located in a specific place at a specific time. ResidenceSafe creates certified proof of presence combining biometric verification, GPS coordinates, and blockchain sealing.
R
-
Residency certificate
A document issued by a country's immigration or government authority confirming that a person holds legal residency status (e.g., a residence permit). Not the same as a Tax Residence Certificate (TRC), which confirms tax residency for treaty purposes. In many jurisdictions, holding a residency certificate still requires proving physical presence thresholds (such as 183 days) for permit renewals.
-
Residency permit
An official authorization granted by a country allowing a foreign national to live there for a defined period. Types include work permits, digital nomad visas, investor visas (Golden Visa), and family reunification permits. Having a residency permit does not automatically make you a tax resident; physical presence tests and other criteria still apply.
Learn more
S
-
Schengen area
A zone of 29 European countries that have abolished internal border controls, allowing free movement of people. Non-EU citizens face the 90/180-day rule. EES will monitor entry/exit at external Schengen borders.
Learn more -
SHA-256
Secure Hash Algorithm producing a 256-bit hash value. Used in blockchain certification to create a unique digital fingerprint of each record. Any alteration to the original data produces a completely different hash, making tampering detectable.
T
-
Tax residence certificate (TRC)
An official document issued by a country's tax authority confirming that a person or entity is a tax resident of that country for a specific period. Used to claim tax treaty benefits and resolve dual residency disputes. NOT the same as a residence permit.
Z
-
Zero tracking
ResidenceSafe's privacy model. Unlike continuous location tracking (which records your position thousands of times per day), zero tracking means no location data is collected between check-ins. One GPS point per check-in. Your movements between check-ins are completely private.
Learn more
Disclaimer. These definitions are for general informational purposes only. Tax and legal terminology varies by jurisdiction and may carry different legal implications depending on context. This content does not constitute legal, tax, or immigration advice. Always consult a qualified professional for your specific situation.
Knowledge is your first defense. ResidenceSafe handles step two.
Understanding tax residency is step one. Proving it is step two. Start building your certified record now.
Also see: 183-day rule · expats guide · how we protect you