September is a time when homeowners with a bed to spare turn into temporary landlords and landladies, welcoming students and professionals in an accommodation fix into their homes, and maybe even serving up a daily meal or two.

Since April, 2001, homeowners can avail of tax relief under the Rent-a-Room scheme, which was introduced in a bid to ease housing pressures. The scheme is intended to help both desperate accommodation-seekers and house buyers who need additional income to help pay their mortgage.

To qualify for the scheme, the person's house or apartment must be his or her main residence. Relief is available up to a maximum of €7,620, including any payment for meals, laundry or other similar services. If the rental income exceeds €7,620, the whole amount is subject to tax.

According to Ms Aoife O'Sullivan, accommodation officer for DCU, this threshold is quite high and shouldn't be a barrier to homeowners who want to rent the room to more than one student.

Students will typically only stay for eight months of the year. This means people renting out "digs" could earn €952 a month tax-free.

The Rent-a-Room scheme is not geared specifically at the student market, however. "It's an incentive to people who have just bought a house to offer students or professionals a room. If you consider you can earn up to €7,620 tax-free, that's a lot of money," says Ms O'Sullivan.

She describes the scheme as an "eye-opener" for new homeowners.

The scheme will not affect full entitlement to capital gains tax relief on the house or apartment if it is subsequently sold. Mortgage interest relief is also unaffected.

A number of people renting out rooms would not have declared their rental income in the past. This made it difficult for tenants to get their rent relief forms signed by the property owner, who might be afraid they would come to the attention of the Revenue.

The fact that income earned by homeowners renting out shared accommodation is often not declared makes it difficult to know how many new lettings the scheme has inspired since its introduction last year.

Homeowners do not have to file a return on last year's income until the tax deadline of October 31st and a spokesman for the Revenue said it would not be able to predict the final number of people who availed of the scheme from early filers.

The scheme has also been criticised by the Union of Students of Ireland (USI), which believes it is a less than ideal solution to accommodation shortages.

The tenants' rights body Threshold has also said that renting a room to support a mortgage could put homeowners in a vulnerable position.

As the Landlord and Tenant Act does not apply in this kind of sharing arrangement, both parties are advised to sign a legally-binding contract, which should include the duration of the agreement, rent and payment dates and the length of notice to quit.