Mid-term rental software: what short-term PMS tools miss

Why short-term tools strain at 30+ nights

Short-term property management systems are built around the night: a nightly rate, a cleaning per turnover and a channel manager that keeps listings in sync across booking sites. Guesty, one of the largest, calls itself vacation rental software and connects to 60+ booking channels. For a holiday operator, that is exactly the right design.

A furnished agency letting for one to eleven months lives on a different clock. Rent is due per month, usually with a part-month at both ends, and every stay rests on a contract, a deposit and often an extension or two. The owner expects a monthly statement, not a list of nightly bookings.

Search results still blur the two. When we checked Google US for "mid term rental software" on 26 October 2026, 4 of the 9 organic results were roundups of short-term rental software (method in "Our data" above).

Some short-term vendors now add a monthly mode. Avantio describes mid-term stays as running from 28 nights up to six months, with monthly billing and a separate deposit for those guests. Its mid-term page does not describe contracts, and in Spain that gap matters: a temporary residential let only starts above 31 days and must state its reason in the contract.

Tax draws a second line at 30 nights. From 1 December 2026, furnished lets of up to 30 nights to the same tenant lose their VAT exemption and carry 10% VAT (art. 7 of RDL 29/2026, if Congress validates it), so your system has to know which side of that line each stay falls on.

The five capabilities to check before you choose

1. Months, not nights

The system should price a stay in calendar months and prorate the first and last month automatically. The same rule has to run through the quote, the tenant invoices and the owner payout.

In Rentamos, full calendar months are charged at the full rent and part-months by days ÷ 30.44 (the average month, 365.25 ÷ 12). Take a stay from 14 March to 10 September 2027 at €1,500 a month: March has 18 days (€886.99), April to August are five full months (€7,500) and September has 10 days (€492.77), so the stay totals €8,879.76.

A nightly tool reaches a different figure for the same stay. At €50 a night (€1,500 ÷ 30), 180 nights come to €9,000; at €49.32 (€1,500 × 12 ÷ 365), they come to €8,876.71. No rule is wrong, but the one in the contract has to be the one in the software, or every first and last invoice turns into a discussion.

2. A contract that states the reason

Since Royal Decree-law 29/2026 (in force since 8 October 2026 and still pending validation by Congress on 26 October 2026), a temporary let in Spain must state the cause that takes the tenant away from their usual home. The cause must be real and provable, and the landlord carries the burden of proof (art. 7.2 LAU, the Spanish tenancy act). A contract without it is treated as a habitual-residence lease, backdated to signature.

The stay must run for more than 31 days and, as a rule, for at most 12 months (art. 9 bis.1 LAU). Your software should generate the contract from a template with the cause filled in, not leave it to a Word file on someone's desktop.

In Rentamos, the contract editor of each booking has a "purpose of the lease" and a "habitual residence" field that fill the template, and you keep one template per language. Rentamos prints what you write; it does not judge whether the cause holds up, which is a question for your lawyer.

3. Deposits and extensions that stay connected

Mid-term tenants extend. If the same parties sign more than two consecutive temporary contracts for the same flat, the first one counts as a habitual-residence lease, with its minimum term and statutory extensions (art. 9 bis.2 LAU). The tool has to show the chain, so you see the third contract coming before anyone signs it.

The deposit should follow the same chain instead of being refunded and charged again at every extension. Any additional guarantee on a temporary let is capped at one month's rent (art. 36.5 LAU as amended). At the end, both parties sign an end-of-tenancy record; without one, the flat is presumed returned in good condition unless proven otherwise (art. 36.7 LAU).

Rentamos treats an extension as a continuation booking. When the same tenant books the same flat within a set window (7 days by default), the booking assistant links it to the previous booking and pre-fills deposit, rent and guests. The earlier booking closes with the deposit retained, and the deposit return with deductions runs on the last booking of the chain.

4. Owners paid and informed

Most furnished agencies let flats on behalf of owners, many of whom live abroad. Look for owner payouts linked to each booking, owner statements as PDF and an owner portal in the owner's language.

Rentamos links owner payouts to bookings, with a per-agency rule for when the first payout falls due: the first of the next month, fixed payout days or when the tenant pays. Owner receipts export as PDF, and the owner portal runs in seven languages: English, Spanish, French, Dutch, Portuguese, German and Polish.

5. One inbox for tenants, owners and leads

Enquiries for mid-term stays arrive by email and WhatsApp, in several languages, often weeks before the move. A shared inbox that links each conversation to the lead, the proposal and later the booking saves the copy-paste between tools.

In Rentamos, Gmail, Outlook and IMAP mailboxes and WhatsApp Business sit in one inbox. A proposal can offer several flats and becomes a booking once the tenant accepts; the tenant then gets a portal of their own in the same seven languages.

What stays the same: cleaning, repairs, handover

Not everything changes at 30 nights. Cleaning between tenants, repair tickets and the check-in still need a schedule and a record, just fewer times a year per flat.

Rentamos covers cleaning tasks with checklists, work orders and maintenance reports with photos. A check-in checklist and an inventory with a tenant walk-through are available in beta. The end-of-tenancy record from art. 36.7 LAU belongs in the same file as the deposit return, whatever tool you use.

Other tools that target monthly stays

Rentamos is not the only option. RentOS describes itself as a property management system for operators of mid-term and long-term furnished rentals, lists lease management and deposit tracking, and says it is free for up to four properties.

Homming, a Spanish rental management tool, has a page for mid-term rentals that lists digital contracts with tenants and owners, its own booking engine and portals for tenants, owners and suppliers. We describe both only from their own pages, checked on 26 October 2026; the table below sets the categories side by side.

Where Rentamos fits, and where it doesn't

Rentamos was built inside Globexs, a furnished rental agency operating in Spain and Belgium since 2002 (our story), for exactly the five jobs above. It fits if 1–11 month furnished lets are your core business, or if you also run longer stays for the same owners.

It is not a channel manager. Rentamos exports an iCal link per property so platforms can block booked dates, but it does not push rates or pull bookings from OTAs.

It does not take card payments online yet; you record transfers and receipts instead. Pricing is quote-based, with no self sign-up, and the legal templates follow Spanish and EU rules, not US or UK tenancy law.

Questions to ask in any demo

• Bill a stay from 14 March to 10 September: what do March and September cost, and does the owner payout use the same rule?
• Where does the contract state the reason for the stay, and in which languages can you generate it?
• Extend that stay twice: does the system show the chain before the third contract, and what happens to the deposit?
• What does the owner see each month, and in which language?
• If I need a channel manager, which one do you connect to, and how?

Do those questions describe your week? Book a free 20-min call and we will run them on a demo account with your own numbers.