Comparing Online and Paper Self-Assessment Tax Returns: Filing Modes for UK Landlords in the MTD Transition Era

For most of the last twenty years the paper-versus-online filing decision has been a real choice. The statutory deadline asymmetry under TMA 1970 section 8 gives online filers three extra months to prepare and submit, and the online portal provides arithmetic validation that paper does not, but paper has remained operationally live for landlords who prefer it, who lack a Government Gateway credential, or who fall inside HMRC's digital-exclusion policy. From 2026 onwards, that balance shifts decisively. Making Tax Digital for Income Tax mandates digital reporting for the largest landlords from 6 April 2026, and HMRC has wound down routine paper-pack distribution since 2022/23.

This page is the filing-mode decision layer for landlords still inside the regular self-assessment universe: those filing for tax years before MTD ITSA mandate bites on their facts, those below the phase 1 (£50,000), phase 2 (£30,000), or phase 3 (£20,000) qualifying-income thresholds, and those with disclosure or property-business profiles that keep them in regular SA rather than MTD ITSA. We set out the deadlines, the operational reality of paper in 2026, the MTD phase-out timeline, the digital-exclusion grounds for staying on paper, and the practical filing-mode benefits and trade-offs that drive the decision.

The statutory deadline asymmetry under TMA 1970 section 8

Section 8 of the Taxes Management Act 1970 sets the personal-return obligation. Subsection (1D) sets the standard deadlines:

• Paper (non-electronic) returns: on or before 31 October in the year following the tax year (Year 2).
• Online (electronic) returns: on or before 31 January in Year 2.

For the 2025/26 tax year (year ending 5 April 2026), the standard deadlines are 31 October 2026 (paper) and 31 January 2027 (online). The three-month gap between the two deadlines is the central statutory benefit of online filing for any landlord whose facts allow either route.

Two exceptions under section 8 adjust the standard deadlines where HMRC issues a late notice to file:

Section 8(1F): Exception 1 (notice given after 31 July, on or before 31 October)

The paper deadline becomes 3 months from the date of the notice. The online deadline remains 31 January. A landlord who receives a first SA notice on 15 August 2026 has until 15 November 2026 on paper or 31 January 2027 online. The 3-month window for paper can be tight where the notice arrives close to the original 31 October cutoff.

Section 8(1G): Exception 2 (notice given after 31 October)

Both paper and online deadlines become 3 months from the date of the notice. The standard online advantage is eliminated. A landlord who receives a first SA notice on 15 November 2026 has until 15 February 2027 on either route. This subsection matters for landlords whose first SA registration coincides with a mid-cycle property acquisition or rental income trigger.

The operational reality of paper filing in 2026

The statutory paper route remains alive, but HMRC's operational distribution model has shifted decisively. Since the 2022/23 cycle, HMRC has not routinely posted SA100 paper packs to anyone in self-assessment. Filers who want a paper pack must request one from the gov.uk paper-pack request page or by phone. The request process takes 5 to 10 working days in normal conditions and longer at peak load close to the 31 October deadline.

HMRC also signposts requesters to the online portal as the default route. Where the requester has a digital-exclusion ground (no internet access, religious exemption, disability), the request should state the ground explicitly. HMRC grants paper packs in genuine cases but the operational presumption is now firmly digital.

The practical consequence: a landlord who plans to file on paper for the 2025/26 tax year should request the pack by early October 2026, give HMRC 10 working days to process the request, and allow a further week to complete and post the return before the 31 October deadline. Leaving the request until mid-October compresses the timeline to the point where paper filing can become operationally infeasible and the landlord ends up filing online anyway, just under more time pressure.

The MTD ITSA phase-out for paper filing

Making Tax Digital for Income Tax is the statutory programme that mandates digital quarterly reporting for landlords and self-employed persons above the qualifying-income threshold. The phases:

• Phase 1: mandate from 6 April 2026 for qualifying income above £50,000.
• Phase 2: mandate from 6 April 2027 for qualifying income above £30,000.
• Phase 3: mandate from 6 April 2028 for qualifying income above £20,000.

Once a landlord is mandated into MTD ITSA, the SA100 paper route is no longer available for the tax years in which they are in scope. The reporting cycle moves to four quarterly updates (covering each three-month accounting period) plus an End of Period Statement (consolidating each business stream) plus a final declaration (replacing the SA100 itself). All four submission types must be made through MTD-recognised software; neither the paper SA100 nor the gov.uk online portal supports MTD ITSA filing.

The reading of the threshold is fact-specific. Qualifying income is gross rental income plus gross self-employed turnover, measured against the relevant prior-but-one tax year's return data. A landlord with £45,000 gross rental in 2024/25 is below phase 1 for 6 April 2026. The same landlord with £55,000 gross rental in 2025/26 may cross phase 1 for the 2026/27 tax year (subject to the precise reading-year convention in the regulations). Filing-mode planning at the bridge years (the last two regular-SA years before mandate) directly determines whether the landlord enters MTD ITSA with or without a workable Government Gateway and software workflow.

Who can still use paper after the MTD phase-out

Four categories remain in the regular-SA universe after MTD ITSA is fully phased in:

• Limited companies. Corporation tax sits in a separate regime that is not in MTD ITSA scope. LtdCo landlords continue to use the CT600 corporation-tax return route via HMRC's CT online filing or commercial CT software.
• Partnerships. MTD ITSA for partnerships has been deferred to a date to be confirmed. Partnerships continue to use SA800 (the partnership return) plus partner-level SA100s; both can be filed on paper or online.
• Trustees. Trustees use SA900 (the trust and estate tax return). MTD ITSA is not extended to trustees in the current phase plan. SA900 can be filed on paper or online but is not MTD-mandated.
• Persons below the relevant phase threshold. Landlords with qualifying income below the current phase threshold continue in regular SA. They can file on paper or online; the SA100 + SA105 paper pack remains operationally available subject to the constrained-distribution caveat above.

A formal digital-exclusion exemption from MTD ITSA itself (separate from the SA paper-filing policy) is also available on similar grounds: no internet access, religious exemption, disability impairing online use. The MTD ITSA exemption framework is more formalised than the SA paper-filing policy and requires a documented application to HMRC.

Digital exclusion: when paper is still appropriate

HMRC's digital-exclusion policy permits paper filing for filers with reasonable-excuse grounds. The policy is HMRC operational discretion applied within section 8 rather than a separate statutory exemption. The recognised grounds are:

• No internet access. The filer has no broadband or mobile data connection at their address and cannot reasonably travel to a public-access internet point.
• Religious exemption. The filer belongs to a religious group whose tenets restrict use of electronic communications (Plymouth Brethren is the most-cited example in HMRC published guidance).
• Disability. The filer has a documented disability that impairs online use (visual impairment without compatible assistive technology, severe motor impairment, cognitive impairment).

Other grounds (age, lack of computer literacy without disability, preference for paper) are not automatic but can be raised informally with HMRC. The decision is HMRC's. If HMRC refuses, the refusal can be challenged via the reasonable-excuse defence under paragraph 23 of Schedule 55 FA 2009 on appeal to the First-tier Tribunal, with the Perrin v HMRC [2018] UKUT 156 four-stage test applied to the underlying facts.

The forms involved on each route

Paper filing

The main return is SA100 (10 to 12 pages). Supplementary pages are added depending on income:

• SA105: UK property income (the principal landlord supplement).
• SA108: capital gains.
• SA106: foreign income including foreign rental property.
• SA110: tax calculation summary (where the filer prepares their own calculation rather than asking HMRC to calculate).

A landlord with a single UK BTL property and no other income complications files SA100 plus SA105 plus SA110 (where calculating themselves). A landlord with a UK BTL plus a Spanish holiday-let property files SA100 plus SA105 plus SA106 plus SA110.

Online filing

Online filing surfaces the same fields through a single integrated guided flow on the gov.uk portal. The portal asks the filer a series of questions to determine which supplementary sections are relevant and then presents the relevant fields. The output is a single submitted return rather than a stapled bundle of supplementary forms, but the underlying data captured is the same as the paper bundle.

Worked example 1: bridge-population single-property landlord

Mr Tasburgh owns 1 BTL flat in Sheffield. Gross rental £8,400 per year; net profit £4,200 after agent fees and repairs. Other income: employed PAYE salary £35,000. Total taxable income around £39,200. He is comfortably below MTD ITSA phase 1 (£50,000) and phase 2 (£30,000 qualifying income); even phase 3 (£20,000 qualifying income, mandate from 6 April 2028) does not catch him because his gross rental income (£8,400) is below the threshold.

Either filing route works statutorily. Paper deadline 31 October 2026; online deadline 31 January 2027. Mr Tasburgh has no Government Gateway credential. Decision drivers:

• Deadline cushion: online buys 3 extra months.
• Operational risk: paper-pack request takes 5 to 10 working days; requesting mid-October would compress the timeline.
• Refund speed: not relevant on his facts (he owes tax rather than is owed a refund).
• MTD continuity: Mr Tasburgh is unlikely to enter MTD scope unless his rental gross grows above £20,000.
• Error-checking: the online portal pre-validates arithmetic and flags missing fields; paper does not.

Recommendation: online, even though paper is statutorily live. The deadline cushion and error-checking benefits outweigh the credential-setup overhead. The credential is a one-time cost paid in the first online cycle; it then carries forward for life and supports an eventual MTD ITSA transition if his rental grows.

Worked example 2: landlord crossing the MTD threshold

Mrs Quainton owns 4 BTL properties. Gross rental £36,000 per year; net profit £18,000. She also runs a self-employed bookkeeping side-business with gross income £6,000. Total qualifying income £36,000 plus £6,000 = £42,000, which is above phase 2 threshold (£30,000 from 6 April 2027).

Filing-mode path: Mrs Quainton files the 2024/25, 2025/26, and 2026/27 returns in the regular SA cycle (either mode statutorily available). From 6 April 2027 onwards she is mandated to MTD ITSA and cannot use the paper SA100 route for 2027/28 or later years while in scope.

Recommendation: start using online SA now (for 2024/25 and onwards). Building the Government Gateway credential, getting comfortable with the online portal, and (if she uses an agent) setting up the Agent Services Account before the 6 April 2027 mandate makes the MTD ITSA transition materially smoother. The quarterly MTD cycle has a steep operational ramp; transitioning from paper SA to MTD ITSA cold is harder than transitioning from online SA to MTD ITSA.

Worked example 3: digital-exclusion case

Mr Hodgekiss is 78, lives in rural Northumberland with no broadband, has never owned a computer, and has a single income source: a small inherited rental property (£5,200 per year net profit) plus his state pension. Total income around £17,000.

HMRC's digital-exclusion policy permits paper filing on his facts (no internet access ground). Operational flow: Mr Hodgekiss requests a paper SA100 pack from gov.uk by phone (the paper-pack request page also accepts phone requests). He files SA100 plus SA105 by 31 October 2026 for the 2025/26 tax year. If HMRC delays processing the request close to the deadline, his reasonable-excuse defence under paragraph 23 of Schedule 55 protects him from the £100 late-filing penalty under the Perrin four-stage test.

Forward path: if MTD ITSA mandate catches Mr Hodgekiss at phase 3 (unlikely on current facts), the digital-exclusion exemption would carry forward to exempt him from MTD ITSA digital requirements as well. The two exemption frameworks (SA paper-filing policy and MTD ITSA digital exemption) are different in formality but built on the same underlying reasonable-excuse logic.

Worked example 4: late-notice scenario under section 8(1F)

Mrs Welwick received an HMRC notice to file on 15 August 2026 (after the 31 July notice-window boundary, before 31 October). She is a new BTL landlord who became chargeable to income tax on rental income in 2025/26 and notified HMRC under section 7 on time.

Section 8(1F) Exception 1 applies: the paper deadline is 3 months from the date of the notice, so 15 November 2026. The online deadline remains 31 January 2027. The standard 3-month gap between paper and online deadlines narrows to around 11 weeks.

Variant: if the notice had instead been given on 15 November 2026 (after 31 October), section 8(1G) Exception 2 would apply and both deadlines would be 3 months from the notice (15 February 2027), eliminating the online advantage entirely. The late-notice subsections matter for any landlord whose first SA notice arrives late in the cycle; the deadline calculation should be checked against the date on the notice itself.

Practical filing-mode benefits and trade-offs

Benefits of online filing

• Deadline cushion: 3 extra months under section 8(1D) standard deadlines.
• Error-checking: the gov.uk portal pre-validates arithmetic and flags missing fields.
• Refund speed: HMRC published guidance puts online refunds at 14 to 21 working days vs 6 to 8 weeks for paper.
• Agent flow: supports the Agent Services Account (ASA) alongside legacy 64-8 paper authorisation; ASA is mandatory for MTD ITSA from 6 April 2026.
• Amendment ease: online amendments within the 12-month statutory window are processed faster than paper amendments.
• MTD continuity: the online credential and software fluency carry forward to MTD ITSA mandate.

Benefits of paper filing

• No credential setup. Useful for first-time filers without a Government Gateway account and without time to set one up.
• No software cost. Online filing is free via gov.uk but commercial tax software for more complex returns has a per-cycle cost.
• Tangible paper trail. Some landlords prefer a physical filing record.
• Accessibility for digital-excluded filers who fit HMRC's policy grounds.

Trade-offs that matter

The paper benefits have narrowed sharply since 2022/23. The credential-setup cost is paid once and carried forward for life; the software-cost concern is mostly irrelevant for a single-property landlord using gov.uk for free; the tangible-paper-trail benefit is matched by online filing's PDF receipt and submission history. The genuine residual case for paper sits with the digital-excluded population, the trustees and partnerships using non-MTD-supported forms, and a narrow cohort of first-time filers who run out of time to set up the Government Gateway before 31 October.

The late-filing penalty asymmetry under Schedule 55 FA 2009

The Schedule 55 £100 initial late-filing penalty attaches to any return submitted after the relevant deadline. The asymmetry between paper and online matters:

• Missed paper deadline (31 October), file online by 31 January: no Schedule 55 penalty. The online deadline saves the return.
• Missed paper deadline, file paper after 31 October: £100 immediate penalty under Schedule 55, even if HMRC receives the envelope a few days later.
• Missed online deadline (31 January): £100 immediate; daily £10 from 3 months late; 5% or £300 at 6 months; further 5% or £300 at 12 months. Same penalty schedule for very-late paper.

The asymmetry is a feature for landlords who originally planned paper but slip past 31 October: they can pivot to online filing and avoid the penalty entirely. It is not a feature for landlords who plan online from the outset: missing 31 January costs £100 immediately on either route.

The Government Gateway credential: a practical checklist

First-time online filers face the credential-setup workflow. The steps:

1. Create a Government Gateway User ID and password at gov.uk/log-in-register-hmrc-online-services. Choose self-assessment as the service.
2. Identity verification: SMS verification plus ID document upload (passport or driving licence) for online-verifiable filers, or activation-code-by-post for filers without a uploadable document.
3. Receive the activation code by post within 7 to 10 working days.
4. Activate the account using the code and the Gateway login.
5. Link the account to self-assessment using the UTR number from any prior HMRC correspondence.

The end-to-end timeline is typically 3 to 4 weeks for a first-time filer with no prior HMRC online account. Leaving the credential setup to mid-January is the most common operational reason for missed 31 January deadlines among first-time online filers. The discipline is to start the credential process in October or November of Year 2, not in late January.

Agent flow: 64-8 vs Agent Services Account

Where the landlord uses a tax adviser, the authorisation flow differs by route:

• Paper filing: the agent uses the 64-8 paper authorisation form. HMRC processes 64-8s manually with a typical turnaround of 2 to 4 weeks.
• Online filing: the agent can use the legacy 64-8 route OR the Agent Services Account (ASA). ASA authorisation is processed electronically within 7 to 10 days.
• MTD ITSA filing (from 6 April 2026 for mandated landlords): only the ASA route works. The legacy 64-8 does not authorise an agent for MTD ITSA.

For a landlord likely to cross the MTD ITSA threshold in the next 2 to 3 years, the agent should be moved onto the ASA flow before the mandate bites. Switching agents at the mandate date with only the legacy 64-8 in place is a recipe for the first MTD quarterly deadline being missed because the agent cannot file on the client's behalf.

The bridge-population recommendation

For most landlords still inside the regular-SA universe in 2026 and 2027, the operational recommendation is online filing, even where paper remains statutorily available. The reasons aggregate:

• The 3-month deadline cushion under section 8(1D).
• The error-checking benefit of the gov.uk portal.
• The faster refund cycle.
• The credential and software fluency that carries forward to MTD ITSA mandate.
• The constrained operational reality of paper-pack distribution.

The exceptions sit with the digital-excluded population (paper remains the right answer on HMRC's published policy grounds), with trustees and partnerships using non-MTD-supported forms, and with first-time filers who genuinely cannot set up a Government Gateway in time for the 31 October paper deadline (and who therefore default to the 31 January online deadline by planning rather than by accident).

If you are weighing a filing-mode decision for the current cycle or planning the bridge-year strategy ahead of MTD ITSA mandate, we work with landlords on the credential setup, the agent-flow choice, and the first-MTD-cycle transition.